calibration and catalyst changes required to address NMOG will also
provide the necessary PM control. Vehicles that currently have higher
PM emissions over the FTP or SFTP at higher mileages will likely be
required to control oil consumption and combustion chamber deposits.
    We also analyzed PM test data results on the US06 test cycle from
Tier 2 vehicles. The data show that many vehicles are already at or
below the Tier 3 standards on the US06 test cycle. Vehicles that have
high PM emission rates on the US06 will likely need to control
enrichment and oil consumption, particularly later in life. As
described above for SFTP NMOG+NOX control, enrichment can be
more accurately managed through available electronic engine controls.
The strategies for reducing oil consumption are similar to those
described above for controlling oil consumption on the FTP. However,
given the higher engine speeds experienced on the US06 and the increase
in oil consumption that can accompany this kind of operation,
manufacturers will most likely focus on oil sources stemming from the
piston to cylinder interface and positive crankcase ventilation (PCV).
    Manufacturers have informed us that they have already reduced or
are planning to reduce the oil consumption of their engines by improved
sealing of the paths of oil into the combustion chamber and improved
piston-to-cylinder interfaces. Auto manufacturers have stated that they
are already taking or considering these actions to address issues of
customer satisfaction and cost of ownership. In addition, many vehicle
manufacturers acknowledge the relationship between combustion chamber
deposits and PM formation and are actively pursuing design changes to
mitigate fuel impingement within the combustion chamber and its
commensurate PM effects. Both types of controls are being widely
applied by manufacturers today.
d. Technologies Manufacturers Are Likely To Apply
    Most of the technologies expected to be applied to light-duty
vehicles to meet the stringent Tier 3 standards will address the
emissions control system's ability to reduce emission during cold start
while maintaining zero or near zero running emissions. The
effectiveness of current vehicle emissions control systems at reducing
cold start emissions depends in large part on the time it takes for the
catalyst to light off, which is typically defined as the catalyst
reaching a temperature of 250 [deg]C. In order to improve catalyst
light-off, we expect that manufacturers will add technologies that
provide heat from combustion more readily to the catalyst or improve
the catalyst efficiency at lower temperatures. These technologies
include calibration changes, catalyst platinum group metals (PGM)
loading and strategy, thermal management, close-coupled catalysts, and
secondary air injection, all which generally improve emission
performance of all pollutants. In some cases where the catalyst light-
off and efficiency are not

enough to address the cold start NMOG emissions, hydrocarbon adsorbers
may be applied to trap hydrocarbons until such time that the catalyst
is lit off. Note that with the exception of hydrocarbon adsorbers each
of these technologies addresses NMOG, NOX, and PM
performance. The technologies are described in greater detail below.
Additional information on these technologies can also be found in
Chapter 1 of the RIA.
     Engine Control Calibration Changes--These include changes
to retard spark and/or adjust air/fuel mixtures such that more
combustion heat is created during the cold start. Control changes may
include injection strategies in GDI applications, unique cold-start
variable valve timing and lift, and other available engine parameters.
Engine calibration changes can affect NMOG, NOX and PM
emissions.
     Catalyst PGM Loading--Additional PGM loading, increased
loading of other active materials, and improved dispersion of PGM and
other active materials in the catalyst provide a greater number of
sites available to catalyze emissions and addresses NMOG,
NOX and PM emissions. Catalyst PGM loading, when implemented
in conjunction with low sulfur gasoline, will effectively eliminate
NOX emissions under warmed-up conditions.
     Thermal Management--This category of technologies includes
all design attributes meant to conduct the combustion heat into the
catalyst with minimal cooling. This includes insulating the exhaust
piping between the engine and the catalyst, reducing the wetted area of
the exhaust path, reducing the thermal mass of the exhaust system, and/
or using close-coupled catalysts (i.e., the catalysts are packaged as
close as possible to the engine's cylinder head to mitigate the cooling
effects of longer exhaust piping). Thermal management technologies
primarily address NMOG emissions, but also affect NOX and PM
emissions.
     Secondary Air Injection--By injecting air directly into
the exhaust stream, close to the exhaust valve, combustion can be
maintained within the exhaust, creating additional heat by which to
increase the catalyst temperature. The air/fuel mixture must be
adjusted to provide a richer exhaust gas for the secondary air to be
effective. There can be a NOX emissions disbenefit to use of
secondary air injection since it can impact the ability of oxygen
storage components (OSC) within the catalyst to take up excess oxygen
as necessary to promote NOX reduction reactions immediately
following cold start conditions.
     Hydrocarbon Adsorber--Traps hydrocarbons during a cold
start until the catalyst lights off, and then releases the hydrocarbons
to be converted by the catalyst.
     Gasoline Sulfur--The relative effectiveness for NMOG and
NOX control of the exhaust-catalyst related technologies is
constrained by gasoline fuel sulfur levels. Thus, reduced sulfur in
gasoline is an enabling technology to achieve the standards and
maintain this performance during in-use operation. We discuss the
relationship between gasoline sulfur and emissions in greater detail in
Section IV.6 below and in the RIA.
    Several commenters indicated that large light-duty trucks (e.g.,
pickups and full-size sport utility vehicles (SUVs) in the LDT3 and
LDT4 categories) will be the most challenging light-duty vehicles to
bring into compliance with the Tier 3 NMOG+NOX standards at
the 30 mg/mi corporate average emissions level. A similar challenge was
addressed when large light-duty trucks were brought into compliance
with the Tier 2 standards over the past decade. Figure IV-1 provides a
graphical representation of the effectiveness of Tier 3 technologies
for large light-duty truck applications. A compliance margin is shown
in both cases. Note that the graphical representation of the
effectiveness of catalyst technologies on NOX and NMOG when
going from Tier 2 to Tier 3 levels also includes a reduction in
gasoline sulfur levels from 30 ppm to 10 ppm.
---------------------------------------------------------------------------

    \261\ The technologies and levels of control in this figure are
based on a combination of confidential business information
submitted by auto manufacturers and suppliers, public data, and EPA
staff engineering judgment.

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[GRAPHIC] [TIFF OMITTED] TR28AP14.000

6. Impact of Gasoline Sulfur Control on the Effectiveness of the
Vehicle Emission Standards
    In this section, we discuss the impact of gasoline sulfur control
on the feasibility of the Tier 3 vehicle emissions standards and on the
exhaust emissions of the existing in-use vehicle fleet. Section
IV.A.6.a describes the chemistry and physics of the impacts of gasoline
sulfur compounds on exhaust catalysts. Sections IV.A.6.b, c and d
summarize research on the impacts of gasoline sulfur on vehicles
utilizing various degrees of emission control technology, with Section
IV.A.6.b summarizing historical studies on the impact of gasoline
sulfur on vehicle emissions, Section IV.A.6.c describing impacts on
Tier 2 vehicles and the existing light-duty vehicle fleet, and Section
IV.A.6.d describing impacts on vehicles using technology consistent
with what we expect to see in the future Tier 3 vehicle fleet. Section
IV.A.6.e provides EPA's assessment of the level of gasoline sulfur
control necessary for light-duty vehicles to comply with Tier 3 exhaust
emission standards.
    EPA's primary findings are:
     Reducing gasoline sulfur content to a 10 ppm average will
provide immediate and significant exhaust emissions reductions to the
current, in-use fleet of light-duty vehicles.
     Reducing gasoline sulfur content to an average of 10 ppm
will enable vehicle manufacturers to certify their entire product lines
of new light-duty vehicles to the final Tier 3 Bin 30 fleet average
standards. Without such sulfur control it would not be possible for
vehicle manufacturers to reduce emissions sufficiently below Tier 2
levels to meet the new Tier 3 standards because it would require
offsetting significantly higher exhaust emissions resulting from the
higher sulfur levels. EPA has not identified any existing or developing
technologies that would compensate for or offset the higher exhaust
emissions resulting from higher fuel sulfur levels.
a. Gasoline Sulfur Impacts on Exhaust Catalysts
    Modern three-way catalytic exhaust systems utilize platinum group
metals (PGM), metal oxides and other active materials to selectively
oxidize organic compounds and carbon monoxide in the exhaust gases.
These systems simultaneously reduce NOX when air-to-fuel
ratio control operates in a condition of relatively low amplitude/high
frequency oscillation about the stoichiometric point. Sulfur is a well-
known catalyst poison. There is a large body of work demonstrating
sulfur inhibition of the emissions control performance of PGM three-way
exhaust catalyst
systems.262 263 264 265 266 267 268 269 270 271

The nature of sulfur interactions with washcoat materials, active
catalytic materials and catalyst substrates is complex and varies with
catalyst composition, exhaust gas composition and exhaust temperature.
The variation of these interactions with exhaust gas composition and
temperature means that the operational history of a vehicle is an
important factor; continuous light-load operation, throttle tip-in
events and enrichment under high-load conditions can all impact sulfur
interactions with the catalyst.
---------------------------------------------------------------------------

    \262\ Beck, D.D., Sommers, J.W., DiMaggio, C.L. (1994). Impact
of sulfur on model palladium-only catalysts under simulated three-
way operation. Applied Catalysis B: Environmental 3, 205-227.
    \263\ Beck, D.D., Sommers, J.W. (1995). Impact of sulfur on the
performance of vehicle aged palladium monoliths.'' Applied Catalysis
B: Environmental 6, 185-200.
    \264\ Beck, D.D., Sommers, J.W., DiMaggio, C.I. (1997). Axial
characterization of oxygen storage capacity in close coupled
lightoff and underfloor catalytic converters and impact of sulfur.
Applied Catalysis B: Environmental 11, 273-290.
    \265\ Waqif, M., Bazin, P., Saur, O. Lavalley, J.C., Blanchard,
G., Touret, O. (1997), Study of ceria sulfation. Applied Catalysis
B: Environmental 11, 193-205.
    \266\ Bazin, P., Saur, O. Lavalley, J.C., Blanchard, G.,
Visciglio, V., Touret, O. (1997). ``Influence of platinum on ceria
sulfation.'' Applied Catalysis B: Environmental 13, 265-274.
    \267\ Takei, Y., Kungasa, Y., Okada, M., Tanaka, T. Fujimoto, Y.
(2000). Fuel Property Requirement for Advanced Technology Engines.
SAE Technical Paper 2000-01-2019.
    \268\ Takei, Y., Kungasa, Y., Okada, M., Tanaka, T. Fujimoto, Y.
(2001). ``Fuel properties for advanced engines.'' Automotive
Engineering International 109 12, 117-120.
    \269\ Kubsh, J.E., Anthony, J.W. (2007). The Potential for
Achieving Low Hydrocarbon and NOX Exhaust Emissions from
Large Light-Duty Gasoline Vehicles. SAE Technical Paper 2007-01-
1261.
    \270\ Shen, Y., Shuai, S., Wang, J. Xiao, J. (2008). Effects of
Gasoline Fuel Properties on Engine Performance. SAE Technical Paper
2008-01-0628.
    \271\ Ball, D., Clark, D., Moser, D. (2011). Effects of Fuel
Sulfur on FTP NOX Emissions from a PZEV 4 Cylinder
Application. SAE Technical Paper 2011-01-0300.
---------------------------------------------------------------------------

    Sulfur from gasoline is oxidized during spark-ignition engine
combustion primarily to SO2 and, to a much lesser extent,
SO3-\2\. Sulfur oxides selectively chemically
bind (chemisorb) with, and in some cases react with, active sites and
coating materials within the catalyst, thus inhibiting the intended
catalytic reactions. Sulfur oxides inhibit pollutant catalysis chiefly
by selective poisoning of active PGM, ceria sites, and the alumina
washcoating material (see Figure IV-2).\272\ The amount of sulfur
retained by an exhaust catalyst system is primarily a function of the
concentration of sulfur oxides in the incoming exhaust gases, air-to-
fuel ratio feedback and control by the engine management system, the
operating temperature of the catalyst and the active materials and
coatings used within the catalyst.
---------------------------------------------------------------------------

    \272\ Heck, R.M., Farrauto, R.J. (2002). Chapter 5: Catalyst
Deactivation in Catalytic Air Pollution Control, 2nd Edition. John
Wiley and Sons, Inc.
---------------------------------------------------------------------------

    In their supplemental comments to the Tier 3 proposal, API
criticized the use of emissions data generated using gasoline with
sulfur content outside of the range of 10 ppm to 30 ppm within EPA and
other analyses of the impacts of gasoline sulfur on exhaust emissions
from current in-use (Tier 2) and future (Tier 3) light-duty vehicles.
Specific examples include:

 Comparisons of exhaust emissions at 5 ppm and 28 ppm gasoline
sulfur levels within the recent EPA study of emissions from Tier 2
vehicles \273\
---------------------------------------------------------------------------

    \273\ The Effects of Ultra-Low Sulfur Gasoline on Emissions from
Tier 2 Vehicles in the In-Use Fleet, EPA-420-R-14-002.
---------------------------------------------------------------------------

 Comparison of exhaust emissions of a SULEV vehicle at 8 ppm
and 33 ppm gasoline sulfur levels within the Takei et al. study \274\
---------------------------------------------------------------------------

    \274\ Takei, Y., Kungasa, Y., Okada, M., Tanaka, T. Fujimoto, Y.
(2000). Fuel Property Requirement for Advanced Technology Engines.
SAE Technical Paper 2000-01-2019.
---------------------------------------------------------------------------

 Comparison of exhaust emissions of a PZEV vehicle at 3 ppm and
33 ppm gasoline sulfur levels within the Ball et al. study.\275\
---------------------------------------------------------------------------

    \275\ Ball, D., Clark, D., Moser, D. (2011). Effects of Fuel
Sulfur on FTP NOX Emissions from a PZEV 4 Cylinder
Application. SAE Technical Paper 2011-01-0300.

    The relationship between changes in gasoline sulfur content and
NOX, HC, NMHC and NMOG emissions is typically linear. The
linearity of sulfur impacts on NOX, NMHC and NMOG emissions
is supported by past studies with multiple fuel sulfur levels all of
which compare gasoline with differing sulfur levels that are below
approximately 100 ppm (e.g., CRC E-60 and 2001 AAM/AIAM programs as
well as comments on this rulemaking submitted by
MECA).276 277 278 An assumption of linearity of the effect
of gasoline sulfur level on catalyst efficiency between any two test
fuels with differing sulfur levels is reasonable given that the mass
flow rate of sulfur in exhaust gas changes in proportion to its
concentration in the fuel, and that the chemistry of adsorption of
sulfur on the active catalyst sites is an approximately-first-order
chemisorption until all active sites within a catalyst reach an
equilibrium state relative to further input of sulfur compounds. The
relative linearity of the effect of gasoline sulfur level on NMOG and
NOX emissions allows exhaust emissions results generated
within EPA and other studies of gasoline sulfur at levels immediately
above or below either 10 ppm or 30 ppm to be normalized to either 10
ppm sulfur (Tier 3 gasoline) or to 30 ppm sulfur (Tier 2 gasoline,
which are used in the analysis of the impacts of the Tier 3 gasoline
standards on existing in-use vehicles and future Tier 3 vehicles.
---------------------------------------------------------------------------

    \276\ Coordinating Research Council. 2003. ``The Effect of Fuel
Sulfur on NH3 and Other Emissions from 2000-2001 Model
Year Vehicles.'' CRC Project No. E-60 Final Report. Accessed on the
Internet on 12/4/2013 at the following URL: http://www.crcao.com/reports/recentstudies2003/E-60%20Final%20Report.pdf.
    \277\ Alliance of Automobile Manufacturers. 2001. ``AAM-AIAM
Industry Low Sulfur Test Program.''
    \278\ Manufacturers of Emission Controls Association. 2013.
``The Impact of Gasoline Fuel Sulfur on Catalytic Emission Control
Systems.''
---------------------------------------------------------------------------

    In their supplemental comments to the Tier 3 proposal, API also
commented that EPA did not show the sulfur impact on exhaust emissions
at intermediate sulfur levels between 10 ppm and 30 ppm. In response,
based on the relative linearity of the effect of gasoline sulfur level
on NMOG and NOX emissions allowing exhaust emissions to be
estimated for gasoline sulfur levels between 10 and 30 ppm, data in
EPA's analysis shows increases NMOG+NOX emissions (as fuel
sulfur increases) that become more severe (i.e., higher percentage
increase in NMOG+NOX emissions) for vehicles with extremely
low \279\ exhaust emission (SULEV, PZEV, LEV III, Tier 3) as described
in further detail in Sections IV.A.6.d and e.
---------------------------------------------------------------------------

    \279\ Vehicles that meet the cleanest emission standards by
demonstrate very low cold start NMOG and NOX emissions
and zero or near-zero running NMOG and NOX emissions.

---------------------------------------------------------------------------

[GRAPHIC] [TIFF OMITTED] TR28AP14.001

---------------------------------------------------------------------------

    \280\ Heck, R.M., Farrauto, R.J. (2002). Chapter 5: Catalyst
Deactivation in Catalytic Air Pollution Control, 2nd Edition. John
Wiley and Sons, Inc.
---------------------------------------------------------------------------

Selective sulfur poisoning of platinum (Pt) and rhodium (Rh) is
primarily from surface-layer chemisorption. Sulfur poisoning of
palladium (Pd) and ceria appears to be via chemisorption combined with
formation of more stable metallic sulfur compounds, e.g. PdS and
Ce2O2S, present in both surface and bulk form
(i.e., below the surface layer).281 282 283 284 Ceria,
zirconia and other oxygen storage components (OSC) play an important
role that is crucial to NOX reduction over Rh as the engine
air-to-fuel ratio oscillates about the stoichiometric closed-loop
control point. \285\ Ceria sulfation interferes with OSC functionality
within the catalyst and thus can have a detrimental impact on the
catalyst's ability to effectively reduce NOX emissions.
Water-gas-shift reactions are important for NOX reduction
over catalysts combining Pd and ceria. This reaction can be blocked by
sulfur poisoning and may be responsible for observations of reduced
NOX activity over Pd/ceria catalysts even with exposure to
fairly low levels of sulfur (equivalent to 15 ppm in
gasoline).286 287 Pd is also of increased importance for
meeting Tier 3 standards due to its unique application in the close-
coupled-catalyst location required for vehicles certifying to very
stringent emission standards. Close-coupling means that the exhaust
catalyst is moved as close as possible to the engine's exhaust ports
within the packaging constraints of an engine compartment. This ensures
that the catalyst reaches its minimal operational, or ``light-off'',
temperature as quickly as possible after the vehicle is started. It
also means, however, that the exhaust catalyst(s) in the close-coupled
location(s) are subject to higher exhaust temperatures during fully-
warmed up operation. Pd is required in closed-coupled catalysts due to
its resistance to high-temperature thermal sintering thereby
maintaining sufficient durability of the emissions control system over
the useful life of a vehicle. Sulfur removal from Pd requires rich
operation at higher temperatures than required for sulfur removal from
other PGM catalysts.
---------------------------------------------------------------------------

    \281\ Luo, T., Gorte, R.J. (2003). A Mechanistic Study of Sulfur
Poisoning of the Water-Gas-Shift Reaction Over Pd/Ceria.'' Catalysis
Letters, 85, Issues 3-4, pg. 139-146.
    \282\ Li-Dun, A., Quan, D.Y. (1990). ``Mechanism of sulfur
poisoning of supported Pd(Pt)/Al2O3 catalysts
for H2-O2 reaction.'' Applied Catalysis 61,
Issue 1, pg. 219-234.
    \283\ Waqif, M., Bazin, P., Saur, O., Lavalley, J.C., Blanchard,
G., Touret, O. ``Study of ceria sulfation.'' Applied Catalysis B:
Environmental 11 (1997) 193-205.
    \284\ Bazin, P., Saur, O., Lavalley, J.C., Blanchard, G.,
Visciglio, V., Touret, O. ``Influence of platinum on ceria
sulfation.'' Applied Catalysis B: Environmental 13 (1997) 265-274.
    \285\ Heck, R.M., Farrauto, R.J. (2002). Chapter 6: Automotive
Catalyst in Catalytic Air Pollution Control, 2nd Edition. John Wiley
and Sons, Inc.
    \286\ Luo, T., Gorte, R.J. (2003) A Mechanistic Study of Sulfur
Poisoning of the Water-Gas-Shift Reaction Over Pd/Ceria. Catalysis
Letters, 85, Issues 3-4, pg. 139-146.
    \287\ Beck, D.D., Sommers, J.W. (1995) Impact of sulfur on the
performance of vehicle aged palladium monoliths. Applied Catalysis
B: Environmental 6, 185-200.
---------------------------------------------------------------------------

    In addition to its interaction with catalyst materials, sulfur can
also react with the wash-coating itself to form alumina sulfate, which
in turn can block coating pores and reduce gaseous diffusion to active
materials below the coating surface (see Figure IV-2).\288\ This may be
a significant mechanism for the observed storage of sulfur compounds at
light and moderate load operation with subsequent, rapid release as
sulfate particulate matter emissions

when high-load, high-temperature conditions are encountered.\289\
---------------------------------------------------------------------------

    \288\ Beck, D.D., Sommers, J.W. (1995) Impact of sulfur on the
performance of vehicle aged palladium monoliths. Applied Catalysis
B: Environmental 6, 185-200.
    \289\ Maricq, M. M., Chace, R.E., Xu, N., Podsiadlik, D.H.
(2002). The Effects of the Catalytic Converter and Fuel Sulfur Level
on Motor Vehicle Particulate Matter Emissions: Gasoline Vehicles.''
Environmental Science and Technology, 36, No. 2 pg. 276-282.
---------------------------------------------------------------------------

    Operating the catalyst at a sufficiently high temperature under net
reducing conditions (e.g., air-to-fuel equivalence that is net fuel-
rich of stoichiometry) can effectively release the sulfur oxides from
catalyst components. Thus, regular operation at sufficiently high
temperatures at net fuel-rich air-to-fuel ratios can minimize the
effects of fuel sulfur levels on catalyst active materials and catalyst
efficiency; however, it cannot completely eliminate the effects of
sulfur poisoning. In current vehicles, desulfurization conditions occur
typically at high loads when there is a degree of commanded enrichment
(i.e., fuel enrichment commanded by the engine management system
primarily for protection of engine and/or exhaust system components). A
study of Tier 2 vehicles in the in-use fleet recently completed by
EPA\290\ shows that emission levels immediately following high speed/
load operation is still a function of fuel sulfur level for the
gasoline used following desulfurization. If a vehicle operates on
gasoline with less than 10 ppm sulfur, exhaust emissions stabilize over
repeat FTP tests at emissions near those of the first FTP that follows
the high speed/load operation and catalyst desulfurization. If the
vehicle continues to operate on higher sulfur gasoline following
desulfurization, exhaust emissions creep upward until a new equilibrium
exhaust emissions level is established. This suggests that lower fuel
sulfur levels achieve emission benefits unachievable by catalyst
desulfurization procedures alone. Continued operation on gasoline with
a 10 ppm average sulfur content or lower is necessary after catalyst
desulfurization in order to achieve emissions reductions with the
current in-use fleet.\291\ Furthermore, regular operation at the high
exhaust temperatures and rich air-to-fuel ratios necessary for catalyst
desulfurization is not desirable and may not be possible for future
Tier 3 vehicles for several reasons:
---------------------------------------------------------------------------

    \290\ The Effects of Ultra-Low Sulfur Gasoline on Emissions from
Tier 2 Vehicles in the In-Use Fleet, EPA-420-R-14-002.
    \291\ See Preamble Section IV.A.6.c and Chapter 1 of the RIA
(Section <IP_ADDRESS>) for more details on this study and its results.
---------------------------------------------------------------------------

     Thermal sintering and resultant catalyst degradation: The
temperatures necessary to release sulfur oxides are high enough to lead
to thermal degradation of the catalyst over time via thermal sintering
of active materials. Sintering reduces the surface area available to
participate in reactions and thus reduces the overall effectiveness of
the catalyst.
     Operational conditions: It is not always possible to
maintain fuel-rich operational conditions and exhaust catalyst
temperatures that are high enough for sulfur removal because of cold
weather, idle conditions and light-load operation.
     Increased emissions: In order to achieve greater emission
reductions across a fuller range of in-use driving conditions, vehicle
manufacturers' use of commanded enrichment, which has been beneficial
for sulfur removal, will be greatly reduced or eliminated under Tier 3.
Additionally, the fuel-rich air-to-fuel ratios necessary for sulfur
removal from active catalytic surfaces would result in increased PM,
NMOG, CO and air toxic emissions, particularly at the high-temperature,
high load conditions (e.g., US06 or comparable) necessary for sulfur
removal. Previously used levels of commanded enrichment (e.g., under
Tier 2) would interfere with the strategies necessary to comply with
more stringent Tier 3 SFTP exhaust emissions standards. There are also
additional provisions within the Tier 3 standards that further restrict
the use of US06 and off-cycle commanded enrichment in an effort to
reduce high-load and off-cycle PM, NMOG, CO and air toxic
emissions.\292\
---------------------------------------------------------------------------

    \292\ See Sec.  86.1811-17 (LD) within the Tier 3 regulations.
Tier 3 restrictions to commanded enrichment are also discussed in
further detail within section IV.A.4.c of this preamble.
---------------------------------------------------------------------------

     Expected changes to engine performance necessary to reduce
fuel consumption and greenhouse gas emissions will improve the thermal
efficiency of engines and may result in reduced exhaust temperatures.
b. Previous Studies of Gasoline Sulfur Impacts
    This section summarizes studies to provide historical context
regarding what is known about the direct impacts of gasoline sulfur on
vehicle exhaust emissions. Reducing fuel sulfur levels has been the
primary regulatory mechanism EPA has used to minimize sulfur
contamination of exhaust catalysts and to ensure optimum emissions
performance over the useful life of a vehicle. The impact of gasoline
sulfur on exhaust catalyst systems has become even more important as
vehicle emission standards have become more stringent. Studies have
suggested a progressive increase in catalyst sensitivity to sulfur when
standards increase in stringency and emissions levels decrease.
Emission standards under the programs that preceded the Tier 2 program
(Tier 0, Tier 1, and National LEV, or NLEV) were high enough that the
impact of sulfur was considered of little importance. The Tier 2
program recognized the importance of sulfur and reduced the sulfur
levels in the fuel from around 300 ppm to 30 ppm in conjunction with
the new emission standards.\293\ At that time, very little work had
been done to evaluate the effect of further reductions in fuel sulfur,
especially on in-use vehicles that may have some degree of catalyst
deterioration due to real-world operation or on vehicles with extremely
low tailpipe emissions as described earlier.
---------------------------------------------------------------------------

    \293\ Tier 2 Regulatory Impact Analysis, EPA 420-R-99-023,
December 22, 1999, last accessed on the Internet on 12/04/2013 at
the following URL: http://epa.gov/tier2.
---------------------------------------------------------------------------

    In 2005, EPA and several automakers jointly conducted a research
program, the Mobile Source Air Toxics (MSAT) Study that examined the
effects of sulfur and other gasoline properties such as benzene and
volatility on emissions from a fleet of nine Tier 2 compliant
vehicles.\294\ The study found significant reductions in
NOX, CO and total hydrocarbons (HC) when the vehicles were
tested on low sulfur fuel, relative to 32 ppm fuel. In particular, the
study found a 48 percent increase in NOX over the FTP when
gasoline sulfur was increased from 6 ppm to 32 ppm. Given the
preparatory procedures related to catalyst clean-out and loading used
by these studies, these results may represent a ``best case'' scenario
relative to what would be expected under more typical driving
conditions. Nonetheless, these data suggested the effect of in-use
sulfur loading was largely reversible for Tier 2 vehicles, and that
there were likely to be significant emission reductions possible with
further reductions in gasoline sulfur level. More recently, EPA
completed a comprehensive study on the effects of gasoline sulfur on
the exhaust emissions of Tier 2 vehicles at low to moderate mileage
levels.\295\ Further details of this study are summarized in Section
IV.A.6.c of this preamble.
---------------------------------------------------------------------------

    \294\ Chapter 6 of the Regulatory Impact Analysis for the
Control of Hazardous Air Pollutants from Mobile Sources Final Rule,
EPA 420-R-07-002, February 2007, last accessed on the Internet on
12/04/2013 at the following URL: http://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P1004LNN.PDF.
    \295\ The Effects of Ultra-Low Sulfur Gasoline on Emissions from
Tier 2 Vehicles in the In-Use Fleet, EPA-420-R-14-002.
---------------------------------------------------------------------------

    In the NPRM, we summarized the limited data available regarding the

impact of gasoline sulfur on the near-zero exhaust emission vehicle
technologies that will be necessary for Tier 3 compliance. Vehicles
certified to California LEV II SULEV and PZEV standards and federal
Tier 2 Bin 2 standards achieve levels of exhaust emissions control
consistent with the levels of control that will be necessary for Tier 3
compliance. While these vehicles represent only a relatively small
subset (e.g., typically small light-duty vehicles and light-duty trucks
with limited GVWR or towing utility) of the broad range of vehicles
that will need to comply with Tier 3 standards as part of a fleet-wide
average, data on these vehicles provide an opportunity to study the
impact of gasoline sulfur on near-zero exhaust emission technologies
and is generally representative of technology that are expected to be
used with mid-size and smaller light-duty vehicles for Tier 3
compliance. Vehicle testing by Toyota (Takei et al.) of LEV I, LEV II
ULEV and prototype SULEV vehicles showed larger percentage increases in
NOX and HC emissions for SULEV vehicles as gasoline sulfur
increased from 8 ppm to 30 ppm, as compared to other LEV vehicles they
tested.\296\ Ball et al. of Umicore Autocat USA, Inc. studied the
impact of gasoline fuel sulfur levels of 3 ppm and 33 ppm on the
emissions of a 2009 Chevrolet Malibu PZEV.\297\ Umicore's testing of
the Malibu PZEV vehicle showed a pronounced and progressive trend of
increasing NOX emissions (referred to as ``NOX
creep'') when switching from a 3 ppm sulfur gasoline to repeated, back-
to-back FTP tests using 33 ppm sulfur gasoline. The PZEV Chevrolet
Malibu, after being aged to an equivalent of 150,000 miles,
demonstrated emissions at a level consistent with the Tier 3 Bin 30
NMOG+NOX standards when operated on 3 ppm sulfur fuel and
for at least one FTP test after switching to 33 ppm certification fuel.
Following operation over 2 FTP cycles on 33 ppm sulfur fuel,
NOX emissions alone were more than double the Tier 3 30 mg/
mi NMOG+NOX standard.\271\ This represents a 70%
NOX increase between 3 ppm sulfur and 33 ppm sulfur
gasolines, approximately 2-3 times of what has been previously reported
for similar changes in fuel sulfur level for Tier 2 and older
vehicles.298 299
---------------------------------------------------------------------------

    \296\ Takei, Y., Kungasa, Y., Okada, M., Tanaka, T. Fujimoto, Y.
(2000). Fuel Property Requirement for Advanced Technology Engines.
SAE Technical Paper 2000-01-2019.
    \297\ Ball, D., Clark, D., Moser, D. (2011). Effects of Fuel
Sulfur on FTP NOX Emissions from a PZEV 4 Cylinder
Application. SAE Technical Paper 2011-01-0300.
    \298\ The Effects of Ultra-Low Sulfur Gasoline on Emissions from
Tier 2 Vehicles in the In-Use Fleet, EPA-420-R-14-002.
    \299\ Shapiro, E. (2009). National Clean Gasoline--An
Investigation of Costs and Benefits. Published by the Alliance of
Automobile Manufacturers.
---------------------------------------------------------------------------

    Both the Umicore and Toyota studies suggest that the emissions from
vehicles using near-zero exhaust emissions control technology similar
to what is expected for compliance with the Tier 3 standards are more
sensitive to changes in gasoline sulfur content at low (sub-30 ppm)
sulfur concentrations than technology used to meet the higher Federal
Tier 2 and California LEV II standards. The Umicore and Toyota studies
clearly indicate that a progressive increase in catalyst sensitivity to
sulfur continues as exhaust emissions decrease from levels required by
federal Tier 2 and California LEV II emissions standards to the lower
levels required by Tier 3 emissions standards. In addition, although
vehicles with Tier 2 technology have somewhat less sulfur sensitivity
compared to future Tier 3 vehicles, there is still significant
opportunity for further emissions reductions from the existing in-use
fleet by reducing gasoline sulfur content from 30 ppm to 10 ppm. The
results of recent testing demonstrating the potential for in-use
emissions reductions from further gasoline sulfur control are
summarized in Section IV.A.6.c. Recent data on the impact of gasoline
sulfur on vehicles with exhaust emission control technologies that we
expect to be used with Tier 3 vehicles is summarized in Sections
IV.A.6.d and e.
c. EPA Testing of Gasoline Sulfur Effects on Tier 2 Vehicles and the
In-Use Fleet
    Both the MSAT \300\ and Umicore \301\ studies showed the emission
reduction potential of lower sulfur fuel on Tier 2 and later technology
vehicles over the FTP cycle. However, assessing the potential for
reduction on the in-use fleet requires understanding how sulfur
exposure over time impacts emissions, and what the state of catalyst
sulfur loading is for the typical vehicle in the field. In response to
these data needs, EPA conducted a new study to assess the emission
reductions expected from the in-use Tier 2 fleet with a reduction in
fuel sulfur level from current levels.\302\ It was designed to take
into consideration what was known from prior studies on sulfur build-up
in catalysts over time and the effect of periodic regeneration events
that may result from higher speed and load operation over the course of
day-to-day driving.
---------------------------------------------------------------------------

    \300\ Chapter 6 of the Regulatory Impact Analysis for the
Control of Hazardous Air Pollutants from Mobile Sources Final Rule,
EPA 420-R-07-002, February 2007, last accessed on the Internet on
12/04/2013 at the following URL: http://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P1004LNN.PDF.
    \301\ Ball, D., Clark, D., Moser, D. (2011). Effects of Fuel
Sulfur on FTP NOX Emissions from a PZEV 4 Cylinder
Application. SAE Technical Paper 2011-01-0300.
    \302\ The Effects of Ultra-Low Sulfur Gasoline on Emissions from
Tier 2 Vehicles in the In-Use Fleet, EPA-420-R-14-002.
---------------------------------------------------------------------------

    The study sample described in this analysis consisted of 93 cars
and light trucks recruited from owners in southeast Michigan, covering
model years 2007-9 with approximately 20,000-40,000 odometer
miles.\303\ The makes and models targeted for recruitment were chosen
to be representative of high sales vehicles covering a range of types
and sizes. Test fuels were two non-ethanol gasolines with properties
typical of certification test fuel, one at a sulfur level of 5 ppm and
the other at 28 ppm. All emissions data was collected using the FTP
cycle at a nominal temperature of 75 [deg]F.
---------------------------------------------------------------------------

    \303\ The NPRM modeling was based on analysis of 81 passenger
cars and trucks. Since the NPRM, twelve additional Tier 2 vehicles
were tested and included in the statistical analysis described in
the docketed final report, examining the effect of sulfur on
emissions from Tier 2 vehicles. The analysis based on the complete
set of 93 Tier 2 vehicles is reflected in the results presented in
this section and the emissions modeling for FRM.
---------------------------------------------------------------------------

    Using the 28 ppm test fuel, emissions data were collected from
vehicles in their as-received state as well as following a high-speed/
load ``clean-out'' procedure consisting of two back-to-back US06 cycles
intended to reduce sulfur loading in the catalyst. A statistical
analysis of this data showed highly significant reductions in several
pollutants including NOX and hydrocarbons, demonstrating
that sulfur loadings have a large effect on exhaust catalyst
performance, and that Tier 2 vehicles can achieve significant
reductions based on removing, at least in part, the negative impact of
the sulfur loading on catalyst efficiency (Table IV-6). For example,
Bag 2 NOX emissions dropped 31 percent between the pre- and
post-cleanout tests on 28 ppm fuel.

                            Table IV-6--Percent Reduction in In-Use Emissions After the Clean-Out Using 28 ppm Test Fuel \a\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           NOX (p-value)   THC (p-value)   CO (p-value)   NMHC (p-value)   CH4 (p-value)   PM (p-value)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Bag 1...................................................  ..............  ..............   6.0% (0.0151)  ..............  ..............           15.4%
                                                                                (< 0.0001)
Bag 2...................................................           31.4%           14.9%  ..............           18.7%           14.4%  ..............
                                                                (0.0003)        (0.0118)                        (0.0131)        (0.0019)
Bag 3...................................................           35.4%           20.4%           21.5%           27.7%           10.3%           24.5%
                                                               (<0.0001)       (<0.0001)        (0.0001)       (<0.0001)       (<0.0001)       (<0.0001)
FTP Composite...........................................           11.4%            3.8%            6.8%            3.5%            6.0%           13.7%
                                                                (0.0002)        (0.0249)        (0.0107)        (0.0498)        (0.0011)       (<0.0001)
Bag 1-Bag 3.............................................  ..............  ..............            7.2%  ..............  ..............  ..............
                                                                                (0.0656)
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ The clean-out effect is not significant at [alpha] = 0.10 when no reduction estimate is provided.

    To assess the impact of lower sulfur fuel on in-use emissions,
further testing was conducted on a representative subset of vehicles on
28 ppm and 5 ppm fuel with accumulated mileage. A first step in this
portion of the study was to assess the differences in the effectiveness
of the clean-out procedure under different fuel sulfur levels. Table
IV-7 presents a comparison of emissions immediately following (<50
miles) the clean-out procedures at the low vs. high sulfur level. These
results show significant emission reductions for the 5 ppm fuel
relative to the 28 ppm fuel immediately after this clean-out; for
example, Bag 2 NOX emissions were 34 percent lower on the 5
ppm fuel vs. the 28 ppm fuel. This indicates that the catalyst is not
fully desulfurized, even after a clean out procedure, as long as there
is sulfur in the fuel. This further indicates that current sulfur
levels in gasoline continue to have a long-term, adverse effect on
exhaust emissions control that is not fully removed by intermittent
clean-out procedures that can occur in day-to-day operation of a
vehicle and demonstrates that lowering sulfur levels to 10 ppm on
average will significantly reduce the effects of sulfur impairment on
emissions control technology.

   Table IV-7--Percent Reduction in Exhaust Emissions When Going From 28 ppm to 5 ppm Sulfur Gasoline for the First Three Repeat FTP Tests Immediately
                                                                   Following Clean-Out
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           NOX (p-value)   THC (p-value)   CO (p-value)   NMHC (p-value)   CH4 (p-value)      PM \a\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Bag 1...................................................            5.3%            6.8%            6.2%            5.7%           14.0%  ..............
                                                                (0.0513)        (0.0053)        (0.0083)        (0.0276)       (<0.0001)
Bag 2...................................................           34.4%           33.9%           (\a\)           26.4%           49.4%  ..............
                                                                (0.0036)       (<0.0001)                        (0.0420)       (<0.0001)
Bag 3...................................................           42.5%           36.9%           14.7%           51.7%           28.5%  ..............
                                                               (<0.0001)       (<0.0001)        (0.0041)       (<0.0001)       (<0.0001)
FTP Composite...........................................           15.0%           13.3%            8.5%           10.9%           23.6%  ..............
                                                                (0.0002)       (<0.0001)        (0.0050)        (0.0012)       (<0.0001)
Bag 1-Bag 3.............................................           (\a\)           (\a\)           (\a\)           (\a\)           (\a\)  ..............
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ The effectiveness of clean-out cycle is not significant at [alpha] = 0.10.

    To assess the overall in-use reduction between high and low sulfur
fuel, a mixed model analysis of all data as a function of fuel sulfur
level and miles driven after cleanout was performed. This analysis
found highly significant reductions for several pollutants, as shown in
Table IV-8. Reductions for Bag 2 NOX were particularly high,
estimated at 52 percent between 28 ppm and 5 ppm overall. For all
pollutants, the model fitting did not find a significant miles-by-
sulfur interaction, suggesting the relative differences were not
dependent on miles driven after clean-out.

                          Table IV-8--Percent Reduction in Emissions From 28 ppm to 5 ppm Fuel Sulfur on In-Use Tier 2 Vehicles
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                NOX+NMOG (p-
                                           NOX (p-value)   THC (p-value)   CO (p-value)   NMHC (p-value)   CH4 (p-value)      value)          PM \a\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Bag 1...................................            7.1%            9.2%            6.7%            8.1%           16.6%             N/A  ..............
                                                (0.0216)        (0.0002)        (0.0131)        (0.0017)      (< 0.0001)
Bag 2...................................           51.9%           43.3%             (a)           42.7%           51.8%             N/A  ..............
                                              (< 0.0001)      (< 0.0001)                        (0.0003)      (< 0.0001)
Bag 3...................................           47.8%           40.2%           15.9%           54.7%           29.2%             N/A  ..............
                                              (< 0.0001)      (< 0.0001)        (0.0003)      (< 0.0001)      (< 0.0001)
FTP Composite...........................           14.1%           15.3%            9.5%           12.4%           29.3%           14.4%  ..............
                                                (0.0008)      (< 0.0001)      (< 0.0001)      (< 0.0001)      (< 0.0001)      (< 0.0001)
Bag 1-Bag 3.............................           (\a\)            5.9%           (\a\)           (\b\)           (\b\)             N/A  ..............
                                                                (0.0074)
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Sulfur level not significant at [alpha] = 0.10.
\b\ Inconclusive because the mixed model did not converge.

    Major findings from this study include:
     Largely reversible sulfur loading is occurring in the in-
use fleet of Tier 2 vehicles and has a measureable effect on emissions
of NOX, hydrocarbons, and other pollutants of interest.
     The effectiveness of high speed/load procedures in
restoring catalyst efficiency is limited when operating on higher
sulfur fuel.
     Reducing fuel sulfur levels from current levels to levels
in the range of the Tier 3 gasoline sulfur standards is expected to
achieve significant reductions in emissions of NOX,
hydrocarbons, and other pollutants of interest in the current in-use
fleet.
     Assuming that the emissions impacts vs. gasoline sulfur
content are approximately linear, changing gasoline sulfur content from
30 ppm to 10 ppm would result in NMOG+NOX emissions
decreasing from 52 mg/mi to 45 mg/mi, respectively (a 13% decrease),
and NOX emissions decreasing from 19 mg/mi to 16 mg/mi,
respectively (a 16% decrease), for the vehicles in the study.
    To evaluate the robustness of the statistical analyses assessing
the overall in-use emissions reduction between operation on high and
low sulfur fuel (Table IV-8), a series of sensitivity analyses were
performed to assess the impacts on study results of measurements from
low-emitting vehicles and influential vehicles, as documented in detail
in the report.\304\ The sensitivity analyses showed that the magnitude
and the statistical significance of the results were not impacted and
thus demonstrated that the results are statistically robust. We also
subjected the design of the experiment and data analysis to a
contractor-led independent peer-review process in accordance with EPA's
peer review guidance. The results of the peer review \305\ \306\
largely supported the study design, statistical analyses, and the
conclusions from the program and raised only minor concerns that have
not changed the overall conclusions and have subsequently been
addressed in the final version of the report.\307\
---------------------------------------------------------------------------

    \304\ The Effects of Ultra-Low Sulfur Gasoline on Emissions from
Tier 2 Vehicles in the In-Use Fleet, EPA-420-R-14-002.
    \305\ Peer Review of the Effects of Fuel Sulfur Level on
Emissions from the In-Use Tier 2 Vehicles, EPA-HQ-OAR-2011-0135-
1847.
    \306\ EPA In-Use Sulfur Report--Response to Peer-Review
Comments, EPA-HQ-OAR-2011-0135-1848.
    \307\ The Effects of Ultra-Low Sulfur Gasoline on Emissions from
Tier 2 Vehicles in the In-Use Fleet, EPA-420-R-14-002.
---------------------------------------------------------------------------

    Overall, the reductions found in this study are in agreement with
other low sulfur studies conducted on Tier 2 vehicles, namely MSAT and
Umicore studies mentioned above, in terms of the magnitude of
NOX and HC reductions when switching from 28 ppm to 5 ppm
fuel.\308\ We have reviewed the results of the emission effects study
performed by SGS, which was included with API's comments on the Tier 3
proposal, and have concluded that these results are also consistent
with the findings of EPA's Tier 2 in-use study, specifically that
exhaust emissions performance is sensitive to fuel sulfur level.\309\
The SGS study also suggests that negative effects of exposure to a
somewhat higher sulfur level (80 ppm in this case) are largely
reversible for Tier 2 vehicles, meaning that reducing fuel sulfur
levels nationwide will bring significant immediate benefits by reducing
emissions of the existing fleet. For further details regarding the Tier
2 In-Use Gasoline Sulfur Effects Study, see the final report.\310\
---------------------------------------------------------------------------

    \308\ Ball, D., Clark, D., Moser, D. (2011). Effects of Fuel
Sulfur on FTP NOX Emissions from a PZEV 4 Cylinder
Application. SAE Technical Paper 2011-01-0300.
    \309\ American Petroleum Institute. 2013. Supplemental Comments
of the American Petroleum Institute. Available in the docket for
this final rule, docket no. EPA-HQ-OAR-2011-0135.
    \310\ The Effects of Ultra-Low Sulfur Gasoline on Emissions from
Tier 2 Vehicles in the In-Use Fleet, EPA-420-R-14-002.
---------------------------------------------------------------------------

    As a follow-on phase to the Tier 2 in-use study, EPA analyzed five
vehicles \311\ certified to Tier 2 Bin 4, LEV II ULEV and LEV II SULEV
exhaust emissions standards to assess the gasoline sulfur sensitivity
of Tier 2 and California LEV II vehicles with emission levels
approaching or comparable to the Tier 3 standards. The analysis found
that these low-emitting Tier 2 vehicles showed similar or greater
sensitivity to fuel sulfur levels compared to the original Tier 2 test
fleet--for example, a 24 percent reduction in FTP composite
NOX emissions when sulfur is reduced from 28 ppm to 5
ppm.\312\ Test results discussed below in section IV.A.6.d also confirm
that there is significantly increased sensitivity of exhaust emissions
to gasoline sulfur as vehicle technologies advance towards exhaust
emissions approaching near-zero emissions (e.g., Tier 3 Bin 50 and
lower). The impact of fuel sulfur on vehicles with exhaust emission
control technologies that we expect to be used with Tier 3 vehicles is
summarized in the next two sections (Preamble IV.A.6.d and e).
---------------------------------------------------------------------------

    \311\ The make and model of the tested vehicles are Honda
Crosstour, Chevrolet Malibu, Chevrolet Silverado, Ford Focus and
Subaru Outback.
    \312\ The Effects of Ultra-Low Sulfur Gasoline on Emissions from
Tier 2 Vehicles in the In-Use Fleet, EPA-420-R-14-002.
---------------------------------------------------------------------------

    EPA believes that the studies by EPA and others described in this
section strongly support our conclusion that reducing gasoline sulfur
content to a 10 ppm average will result in significant exhaust
emissions reductions from the current in-use fleet. However, some
commenters have expressed concerns about the relevance and
appropriateness of the data, as well as the conclusions drawn from
them. The Summary and Analysis of Comments document, available in the
docket for this rulemaking, provides our responses to those comments.
d. Testing of Gasoline Sulfur Effects on Vehicles With Tier 3/LEV III
Technology
    The Tier 3 fleet average exhaust emissions standards of 30 mg/mi
NMOG+NOX will require large reductions of emissions across a
broad range of light-duty vehicles and trucks with differing degrees of
utility. Previous studies of sulfur impacts on extremely low exhaust
emission vehicles (e.g., Toyota, Umicore) were limited to mid-size or
smaller light-duty vehicles. There are currently no LDT3 or any LDT4
vehicles certified at or below Federal Tier 2 Bin 3 or to the
California LEV II SULEV exhaust emission standards with the exception
of a single hybrid electric SUV. At the time of the Tier 3 NPRM, EPA
was not aware of any existing data demonstrating the impact of changes
in gasoline sulfur content on larger vehicles with technology
comparable to what would be expected for compliance with Tier 3 exhaust
emission standards. In their supplemental comments to the Tier 3
proposal, API criticized EPA's reliance on emissions data from older
vehicles that were not considered to be examples of future Tier-3-like
vehicles. In order to further evaluate this issue, the Agency initiated
a test program at EPA's National Vehicle and Fuel Emissions Laboratory
(NVFEL) in Ann Arbor, Michigan. The Agency obtained a heavy-light-duty
truck and applied changes to the design and layout of the exhaust
catalyst system and to the calibration of the engine management system
consistent with our engineering analyses of technology necessary to
meet Tier 3 Bin 30 emissions with a 20 to 40% compliance margin at
150,000 miles. EPA also requested that Umicore loan the Agency the
vehicle tested in their study to undergo further evaluation of gasoline
sulfur impacts on exhaust emissions. In addition, Ford Motor Company
completed testing of fuel sulfur effects on a Tier 3/LEV III
developmental heavy-light-duty truck and submitted a summary report of
their

findings as part of their supplemental comments to the Tier 3 NPRM. The
results of these three test programs are summarized below.
i. Ford Motor Company Tier 3 Sulfur Test Program
    Ford Motor Company recently completed testing of a heavy-light-duty
truck (i.e., between 6,000 and 8,500 pounds GVWR) under development to
meet the Tier 3 Bin 50 standards on two different fuel sulfur levels
and submitted the resulting data to EPA as part of its supplemental
comments.313 314 The test results from this vehicle are
particularly important when considering the following factors:
---------------------------------------------------------------------------

    \313\ Ford Motor Company. 2013. ``Quality Changes Needed to Meet
Tier 3 Emission Standards and Future Greenhouse Gas Requirements.''
Attachment 2: ``Tier 3 Sulfur Test Program--Ford Motor Company
Summary Report.'' Available within EPA Docket for this final rule,
EPA-HQ-2011-0135.
    \314\ Dominic DiCicco, Ford Motor Company. 2013. ``Additional
data as requested. RE: Ford Supplemental Comments on Tier 3.''
Available within EPA Docket for this final rule, EPA-HQ-2011-0135.
---------------------------------------------------------------------------

     These are the first detailed emissions data submitted by a
vehicle manufacturer to the Agency demonstrating emissions of a heavy-
light-duty-truck consistent with Tier 3 Bin 50 or lower emissions
levels.
     The truck tested uses a version of Ford's 2.0 L GTDI
engine, an engine with high BMEP (approximately 23-bar) that can allow
significant engine displacement downsizing while maintaining the
truck's utility. This is a key enabling GHG reduction strategy analyzed
by EPA in the 2017-2025 GHG Final Rule.\315\
---------------------------------------------------------------------------

    \315\ See 77 FR 62840-62862, October 15, 2012; and Joint
Technical Support Document: Final Rulemaking for 2017-2025 Light-
Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average
Fuel Economy Standards (EPA-420-R-12-901), August 2012, Chapter
<IP_ADDRESS>-<IP_ADDRESS> (pages 3-88--3-95).
---------------------------------------------------------------------------

     The vehicle was specifically under development by a
vehicle manufacturer with an engineering target of meeting Tier 3 Bin
50 and LEV III ULEV50 exhaust emissions standards.
Turbocharged, downsized engines are key technologies within Ford's
strategy to reduce GHG emissions.\316\ EPA expects that trucks with
configurations similar to this developmental Ford Explorer (downsized
engines with reduced GHG emissions and very low emissions of
NMOG+NOX) will become increasingly prevalent within the
timeframe of the implementation of the Tier 3 regulations.
---------------------------------------------------------------------------

    \316\ Ford Motor Company, 2012. ``Sustainability 2011/2012--
Improving Fuel Economy.'' Accessed on the Internet on 11/21/2013 at:
http://corporate.ford.com/microsites/sustainability-report-2011-12/environment-products-plan-economy. Available within EPA Docket for
this final rule, EPA-HQ-2011-0135.
---------------------------------------------------------------------------

    The developmental truck used close-coupling of both catalyst
substrates and relatively high PGM loading (150 g/ft\3\). Ford used
accelerated aging of the catalysts and O2 sensors to an
equivalent of 150,000 miles (the Tier 3 full useful life). The
developmental hardware and engine management calibration configuration
of this truck was designed to meet federal Tier 3 Bin 50 and California
LEV III ULEV50 standards of 50 mg/mi NMOG+NOX at 150,000
miles. The emissions data submitted by Ford included NOX and
NMHC emissions during operation on E10 California LEV III certification
fuel at two different sulfur levels, 10 ppm and 26.5 ppm. Ford did not
provide NMOG emissions data but there was sufficient information for
EPA to calculate NMOG emissions from the provided NMHC data using
calculations from Title 40 CFR 1066.665.
    The truck demonstrated average FTP NMOG+NOX emissions of
37 mg/mi on the 10 ppm E10 California LEV III fuel, emissions that are
consistent with compliance with Bin 50 and ULEV50 standards with a
reasonable margin of compliance (emissions at approximately 70% of the
standard). Retesting of the same vehicle on LEV3 E10 blended \317\ to
26.5 ppm S resulted in average NMOG+NOX emissions of 53 mg/
mi, 6% above the Tier 3 Bin 50 standard. Ford found a high level of
statistical significance with respect to the increase of emissions with
increasing fuel sulfur. Assuming a linear effect of sulfur on emissions
performance, NMOG+NOX emissions would be approximately 56
mg/mi at 30 ppm sulfur, which is approximately 12% above the Bin 50
exhaust emissions standard. This also represents an increase in
NMOG+NOX emissions of 53% with an approximate doubling of
NOX emissions and a 13% increase in NMOG for 30 ppm sulfur
gasoline vs. 10 ppm sulfur gasoline.
---------------------------------------------------------------------------

    \317\ Ford used the same tert-butyl sulfide fuel sulfur
additives used within the EPA testing in IV.A.6.c and d.
---------------------------------------------------------------------------

    The advanced technology Ford truck, which was shown to be capable
of complying with the Tier 3 Bin 50 standard with a reasonable margin
of compliance on 10 ppm sulfur gasoline, in effect reverted to
approximately LEV II ULEV exhaust emissions levels when tested on
higher sulfur gasoline, equivalent to the previous level of emissions
control to which earlier models of this vehicle were certified for MY
2013. The effect of increasing gasoline sulfur levels from 10 ppm to 30
ppm \318\ on this vehicle essentially negated the entire benefit of the
advances in emissions control technology that were applied by the
vehicle manufacturer to meet developmental goals for compliance with
Tier 3 standards. This clearly indicates, for this vehicle model using
technology representative of what would be expected for compliance with
Tier 3 Bin 50 and post 2017 GHG standards, reducing gasoline sulfur to
10 ppm is needed for the advances in technology to achieve their
intended effectiveness in reducing NMOG+NOX emissions. The
advances in vehicle technology and the reduction in gasoline sulfur
clearly are both needed to achieve the emissions reductions called for
by Tier 3.
---------------------------------------------------------------------------

    \318\ Emissions at 30 ppm sulfur estimated assuming
approximately linear emissions effects between 10, 26.5 and 30 ppm
gasoline sulfur levels.
---------------------------------------------------------------------------

ii. EPA Re-Test of Umicore 2009 Chevrolet Malibu PZEV
    Ball et al. of Umicore Autocat USA, Inc. previously studied the
impact of gasoline fuel sulfur levels of 3 ppm and 33 ppm on the
emissions of a 2009 Chevrolet Malibu PZEV.\319\ In their supplemental
comments, API commented that the composition of the two test fuels
outside of sulfur content was not held constant and thus the exhaust
emissions differences attributed to the difference in gasoline sulfur
levels may have been due to other fuel property differences. For
example, the 3 ppm fuel used by Ball et al. was nonoxygenated EEE Clear
test fuel (essentially, Tier 2 Federal certification gasoline except
with near-zero sulfur) while the 33 ppm fuel was an oxygenated
California Phase 2 LEV II certification fuel. Thus it was not entirely
clear if the changes in NOX emissions observed between tests
with the two fuels were significantly impacted by fuel composition
variables other than gasoline sulfur content. EPA obtained the same
test vehicle from Umicore for retesting at the EPA NVFEL facility using
the 5 ppm and 28 ppm sulfur E0 test fuels and vehicle test procedures
used in EPA gasoline sulfur effects testing on Tier 2 vehicles (see
Section IV.6.b).
---------------------------------------------------------------------------

    \319\ Ball, D., Clark, D., Moser, D. (2011). Effects of Fuel
Sulfur on FTP NOX Emissions from a PZEV 4 Cylinder
Application. SAE Technical Paper 2011-01-0300. Available in the
docket for this final rule.
---------------------------------------------------------------------------

    In EPA's retest of the 2009 Chevrolet Malibu PZEV, when sulfur was
the only difference between the test fuels, the gasoline with higher
sulfur resulted in significantly higher increases in NOX
emissions with increasing fuel sulfur content than was observed in the

previous testing by Ball et al. at Umicore. Assuming emissions impacts
vs. gasoline sulfur content are approximately linear, the original data
from Ball et al. would have resulted in a predicted increase in
NOX emissions of approximately 40% when increasing gasoline
sulfur from 10 ppm to 30 ppm. The EPA re-testing of the same vehicle
that controlled for other fuel composition differences resulted in a
predicted increase in NOX emissions of 93% when increasing
gasoline sulfur from 10 ppm to 30 ppm, with NOX emissions
approximately doubling from 22 g/mi to 43 g/mi, with no statistically
significant difference in NMOG emissions and with an increase in
NMOG+NOX emissions of 56%. The approximate doubling in
NOX emissions with the Malibu PZEV between 10 ppm and 30 ppm
sulfur was nearly identical to the results found during testing of the
Tier 3 Bin 50 developmental Ford Explorer discussed above. The results
confirm that fuel compositional differences other than sulfur may have
impacted exhaust emissions results in the Ball et al. study by
underreporting a substantial portion of the effect of increased sulfur
on NOX emissions. When controlling for other fuel
composition differences, the resultant increase in NOX
exhaust emissions due to increasing gasoline sulfur was more than
double that observed in the original Ball et al. study. The observed
increase in NMOG+NOX emissions during EPA testing of the
Malibu PZEV was also comparable to results found with the developmental
Tier 3 Bin 50 Ford Explorer. There was also a much higher increase in
NOX and NMOG+NOX emissions for both the Malibu
PZEV and the Tier 3 Bin 50 Explorer with increased gasoline sulfur than
was observed with Tier 2 vehicles in the EPA Tier 2 in-use study. (See
also Chapter 1.2.4 of the RIA)
iii. EPA Prototype Tier 3 Heavy-Light-Duty Truck Test Program
    EPA purchased a 2011 Chevrolet Silverado heavy-light-duty (LDT4)
pickup truck with a developmental goal of modifying the truck to
achieve exhaust emissions consistent with compliance with the Tier 3
Bin 30 emissions standards. The truck was equipped with a 5.3L V8 with
General Motors' ``Active Fuel Management'' cylinder deactivation
system. This particular truck was chosen in part because cylinder
deactivation is a key technology for light-truck compliance with future
GHG standards and in part because it achieved very low emissions in its
OEM, Tier 2-compliant configuration (certified to Tier 2 Bin 4). A
prototype exhaust system was obtained from MECA consisting of high-
cell-density (900 cpsi) thin-wall (2.5 mil), high-PGM, close-coupled
Pd-Rh catalysts with an additional under-body Pd-Rh catalyst. The total
catalyst volume was approximately 116 in\3\ with a specific PGM loading
of 125 g/ft\3\ and approximate loading ratio of 0:80:5 (Pt:Pd:Rh).
Third-party (non-OEM) EMS calibration tools were used to modify the
powertrain calibration in an effort to improve catalyst light-off
performance. The final test configuration used approximately 4 degrees
of timing retard and approximately 200 rpm higher idle speed relative
to the OEM configuration during and immediately following cold-start.
The exhaust catalyst system and HEGO sensors were bench aged to an
equivalent 150,000 miles using standard EPA accelerated catalyst bench-
aging procedures.\320\ The truck was tested on California LEV III E10
certification fuel at 9 and 29 ppm gasoline sulfur levels.
---------------------------------------------------------------------------

    \320\ U.S. Code of Federal Regulations, Title 40, Sec.  86.1823-
08 ``Durability demonstration procedures for exhaust emissions.''
---------------------------------------------------------------------------

    The EPA Tier 3 prototype Silverado achieved NMOG+NOX
emissions of 18 mg/mi on the 9 ppm S fuel. The NMOG+NOX
emissions were approximately 60% of the Bin 30 standard and thus are
consistent with meeting the Tier 3 Bin 30 exhaust emissions standard
with a moderate compliance margin. NMOG+NOX emissions
increased to 29 mg/mi on the 29 ppm S fuel and one out of four tests
exceeded the Bin 30 exhaust emissions standards. NMOG+NOX
emissions would be at 19 mg/mi and 30 mg/mi with 10 ppm and 30 ppm
gasoline sulfur, respectively, assuming a linear effect of sulfur on
emissions performance. This represents an increase in
NMOG+NOX emissions of approximately 55%, comparable to
increases observed with both the EPA-tested Chevrolet Malibu PZEV and
the developmental Tier 3 Bin 50 Ford Explorer. The impact of increased
gasoline sulfur on NMOG+NOX emissions was due to comparable
increases (on a percentage basis) in both NMOG and NOX
emissions. This effect of gasoline sulfur on the Prototype Silverado
truck's emissions differed from the sulfur impacts observed on the
developmental Ford Explorer, which primarily affected NOX
emissions, and the Malibu PZEV, where the impact was entirely on
NOX emissions.
e. Gasoline Sulfur Level Necessary for New Light-Duty Vehicles To
Achieve Tier 3 Exhaust Emissions Standards
    Meeting Tier 3 NMOG+NOX standards will require major
reductions in exhaust emissions across the entire fleet of new light-
duty vehicles. As discussed in previous sections, the Tier 3 program
will require reductions in fleet average NMOG+NOX emissions
of over 80 percent for the entire fleet of light-duty vehicles and
light-duty trucks. This significant level of fleet average emission
reduction will require reductions from all parts of the fleet,
including vehicles models with exhaust emissions currently at or near
the level of the fully phased-in Tier 3 FTP NMOG+NOX fleet
average standard of 30 mg/mi.
    Compliance with the more stringent Tier 3 fleet average standards
will require vehicle manufacturers to certify a significant amount of
vehicles to bin standards that are below the Bin 30 fleet average
standard to offset other vehicles that are certified to bin standards
that remain somewhat above the Bin 30 fleet average even after
significantly reducing their emissions. At the same time, the
stringency of the Tier 3 standards will push almost all vehicle models
to be close to or below the Bin 30 fleet average standard. There are
only 2 compliance bins below Bin 30, i.e., Bin 20 and Bin 0, available
to offset emissions of vehicles certifying above Bin 30. There is also
very limited ability for vehicle manufacturers to certify vehicles
below the stringent Tier 3 fleet average exhaust emissions standard
since Bin 20 and Bin 30 standards for individual vehicle certification
test groups are approaching the engineering limits of what can be
achieved for vehicles using an internal combustion engine and Bin 0 can
only be achieved by electric-only vehicle operation. The result is that
there is a very limited ability to offset sales of vehicles certified
above the 30 mg/mi fleet average emission standard. This means in
general that vehicle models currently with higher emissions will have
to achieve significant emissions reductions to minimize the gap, if
any, between their certified bin levels under Tier 3 and the Tier 3 Bin
30 fleet average standard, and vehicle models currently at or below Bin
30 will also have to achieve further emissions reductions under Tier 3
to offset the vehicles that remain certified to bin standards somewhat
above Bin 30l. The end result is a need for major reductions from all
types of vehicles in the light-duty fleet, including those above as
well as most vehicles that are already near, at, or

below the Tier 3 Bin 30 fleet average standard.
    Achieving exhaust emissions reductions of over 80% for the fleet,
with major reductions across all types of light-duty vehicles and
light-duty trucks, will be a major technological challenge. Vehicles
already have made significant advances in controlling cold start
emissions and maximizing exhaust catalyst efficiency (e.g., improving
warm-up and catalyst light-off after cold starts and maintaining very
high catalyst efficiency once warmed up) in order to meet Tier 2 and
LEV II emissions standards. There are no ``low-hanging fruit''
remaining for additional NMOG+NOX reductions from light-duty
vehicles from a technology perspective, meaning that vehicle
manufacturers cannot merely change one aspect of emissions control and
thereby achieve all of the required reductions. Instead, compliance
with light-duty Tier 3 exhaust emissions standards will require
significant improvements in all areas of emissions control--with
further improvements in fuel-system management and mixture preparation
during cold start, improvements in achieving catalyst light-off
immediately after cold start, and improved catalyst efficiency during
stabilized, fully-warmed-up conditions. Manufacturers will need further
improvements in each of these areas with nearly every vehicle in order
to comply with the fleet-average Tier 3 standards.
    From a technology perspective, the most likely control strategies
will involve using exhaust catalyst technologies and powertrain
calibration primarily focused on reducing cold-start emissions of NMOG,
and on reducing both cold-start and warmed-up (running) emissions of
NOX. An important part of this strategy, particularly for
larger vehicles having greater difficulty achieving cold-start NMOG
emissions control, will be to reduce NOX emissions to near-
zero levels. This will involve controlling engine-out NOX
emissions during cold start, shortening the cold start period prior to
catalyst light-off of NOX reduction reactions, and better
controlling NOX emissions once the catalyst is fully warmed
up. This is needed to allow a sufficient NMOG compliance margin so that
vehicles can meet the combined NMOG+NOX emissions standards
for their full useful life.
    While significant NMOG+NOX emissions reductions can be
achieved from better control of cold start NMOG emissions, there are
practical engineering limits to NMOG control for larger displacement
vehicles (e.g., large light-duty trucks with significant payload and
trailer towing capabilities). This is based in part on the impact on
NMOG emissions of the larger engine surface-to-volume ratio and
resultant heat conduction from the combustion chamber during warm-up.
There are also tradeoffs between some cold-start NMOG controls and
cold-start NOX control. For example, secondary air injection
and/or leaner fueling strategies improve catalyst light-off for NMOG
after a cold-start but also place OSC components in an oxidation state
that limits potential for NOX reduction and thus often
result in higher cold-start NOX emissions. Some applications
achieve lower NMOG+NOX emissions without the use of
secondary air injection by careful calibration, changes to the catalyst
formulation and balancing of catalyst HC and NOX activity.
The EPA Prototype Silverado and the developmental Ford Explorer are
specific examples of this approach.
    Because of engineering limitations with large vehicles, heavy-
light-trucks and other vehicles with significant utility, we expect
many applications will need close to 100% efficiency in NOX
control under fully warmed-up conditions and very fast light-off of
NOX reduction reactions over the exhaust catalyst almost
immediately after cold-start for those applications. This will require
significant improvements in catalytic and engine-out NOX
reduction compared with Tier 2 vehicles and will be especially
important for heavier vehicles due to the challenges of achieving low
NMOG.
    These technology improvements--improving warm-up and catalyst
light-off after cold starts and maintaining very high catalyst
efficiency--once warmed up--all rely on 10 ppm average sulfur fuel to
achieve the very significant emissions reductions required for the
fleet to achieve the Tier 3 Bin 30 fleet average emissions standard.
The evidence from the test results and specific vehicle examples
discussed above clearly indicate that leaving the gasoline sulfur level
at 30 ppm would largely negate the benefits of key technology
improvements expected to be used for compliance with Tier 3 exhaust
emissions standards. Without the lower 10 ppm gasoline sulfur content,
the Tier 3 exhaust fleet average emissions standards would not be
achievable across the broad range of vehicles that must achieve
significant exhaust emissions reductions.
    One aspect of the need for sulfur levels of 10 ppm average stems
from the fact that achieving the Tier 3 emission standards will require
very careful control of the exhaust chemistry and exhaust temperatures
to ensure high catalyst efficiency. The impact of sulfur on OSC
components in the catalyst makes this a challenge even at relatively
low (10 ppm) gasoline sulfur levels. NOX conversion by
exhaust catalysts is strongly influenced by the OSC components like
ceria. Ceria sulfation may play an important role in the large
degradation of NOX emission control with increased fuel
sulfur levels observed in the MSAT, Umicore and EPA Tier 2 In-Use
Gasoline Sulfur Effects studies and the much more severe NOX
emissions degradation observed in recent test data from PZEV and
prototype/developmental Tier 3/LEV III vehicles.\321\
---------------------------------------------------------------------------

    \321\ Heck, R.M., Farrauto, R.J. (2002). Chapter 6: Automotive
Catalyst in Catalytic Air Pollution Control, 2nd Edition. John Wiley
and Sons, Inc.
---------------------------------------------------------------------------

    The importance of lower sulfur gasoline is also demonstrated by the
fact that vehicles certified to California SULEV are typically
certified to higher bins for the federal Tier 2 program. Light-duty
vehicles certified to CARB SULEV and federal Tier 2 Bin 2 exhaust
emission standards accounted for approximately 3.1 percent and 0.4
percent, respectively, of vehicle sales for MY2009. Light-duty vehicles
certified to SULEV under LEV II are more typically certified federally
to Tier 2 Bin 3, Bin 4 or Bin 5, and vehicles certified to SULEV and
Tier 2 Bins 3-5 comprised approximately 2.5 percent of sales for
MY2009. In particular, nonhybrid vehicles certified in California as
SULEV are not certified to federal Tier 2 Bin 2 emissions standards
even though the numeric limits for NOX and NMOG are shared
between the California LEV II and federal Tier 2 programs for SULEV and
Bin 2. Confidential business information shared by the auto companies
indicate that the primary reason is an inability to demonstrate
compliance with SULEV/Bin 2 emission standards after vehicles have
operated in-use on gasoline with greater than 10 ppm sulfur and with
exposure to the higher sulfur gasoline sold nationwide. While vehicles
certified to the LEV II SULEV and Tier 2 Bin 2 standards both
demonstrate compliance using certification gasoline with 15-40 ppm
sulfur content, in-use compliance of SULEV vehicles in California
occurs after significant, sustained operation on gasoline with an
average of 10 ppm sulfur and a maximum cap of 30 ppm sulfur while
federally certified vehicles under the Tier 2 program operate on
gasoline with an average of 30 ppm sulfur and a maximum cap of 80 ppm
sulfur. Although the SULEV and Tier 2 Bin 2

standards are numerically equivalent, the increased sulfur exposure of
in-use vehicles certified under the federal Tier 2 program results in a
need for a higher emissions compliance margin to take into account the
impact of in-use gasoline sulfur on full useful life vehicle emissions.
As a result, vehicles certified to California SULEV typically certify
to emissions standards under the federal Tier 2 program that are 1-2
certification bins higher (e.g., SULEV certified federally as Tier 2
Bin 3 or Bin 4) in order to ensure in-use compliance with emissions
standards out to the full useful life of the vehicle when operating on
higher-sulfur gasoline.
    There are currently no LDTs larger than LDT2 with the exception of
a single hybrid electric SUV certified to Tier 2 Bin 2 or SULEV
emissions standards. We expect that additional catalyst technologies,
for example increasing catalyst surface area (volume or substrate cell
density) and/or increased PGM loading, will need to be applied to
larger vehicles in order to achieve the catalyst efficiencies necessary
to comply with the Tier 3 standards, and any sulfur impact on catalyst
efficiency will have a larger impact on vehicles and trucks that rely
more on very high catalyst efficiencies in order to achieve very low
emissions. The vehicle emissions data referenced in Section IV.A.6.d
represents the only known data on non-hybrid vehicles spanning a range
from mid-size LDVs to heavy-light-trucks at the very low criteria
pollutant emissions levels that will be needed to comply with the Tier
3 exhaust emissions standards. The developmental Ford Explorer,
Chevrolet Malibu PZEV and EPA prototype Chevrolet Silverado vehicles
described in section IV.A.6.c also represent a range of different
technology approaches to both criteria pollution control and GHG
reduction (e.g., use of secondary air vs. emphasizing cold-start
NOX control, use of engine downsizing via turbocharging vs.
cylinder deactivation for GHG control, etc.) and represent a broad
range of vehicle applications and utility (mid-size LDV, LDT3, LDT4).
All of the vehicles with Tier 3/LEV III technology demonstrated greater
than 50% increases in NMOG+NOX emissions when increasing
gasoline sulfur from 10 ppm to 30 ppm. Two of the vehicles showed a
doubling of NOX emissions when increasing gasoline sulfur
from 10 ppm to 30 ppm. Both of the heavy-light-duty trucks with
specific engineering targets of meeting Tier 3 emissions were capable
of meeting their targeted emission standards with a sufficient
compliance margin on 10 ppm sulfur gasoline and could not meet their
targeted emissions standards or could not achieve a reasonable
compliance margin when tested with 30 ppm sulfur gasoline.
    The negative impact of gasoline sulfur on catalytic activity and
the resultant loss of exhaust catalyst effectiveness to chemically
reduce NOX and oxidize NMOG occur across all vehicle
categories. However, the impact of gasoline sulfur on the effectiveness
of exhaust catalysts to control NOX emissions in the fully-
warmed-up condition is particularly of concern for larger vehicles (the
largest LDVs and LDT3s, LDT4s, and MDPVs). Manufacturers face the most
significant challenges in reducing cold-start NMOG emissions for these
vehicles. Because of the need to reach near-zero NOX
emissions levels in order to offset engineering limitations on further
NMOG exhaust emissions control with these vehicles, any significant
degradation in NOX emissions control over the useful life of
the vehicle would likely prevent some if not most larger vehicles from
reaching a combined NMOG+NOX level low enough to comply with
the 30 mg/mi fleet-average standard. Any degradation in catalyst
performance due to gasoline sulfur would reduce or eliminate the margin
necessary to ensure in-use compliance with the Tier 3 emissions
standards. Certifying to a useful life of 150,000 miles versus the
current 120,000 miles will further add to manufacturers' compliance
challenge for Tier 3 large light trucks (See Section IV.A.7.c below for
more on the useful life requirements.) These vehicles represent a
sufficiently large segment of light-duty vehicle sales now and for the
foreseeable future such that their emissions could not be sufficiently
offset (and thus the fleet-average standard could not be achieved) by
certifying other vehicles to bins below the fleet average standard.
    As discussed above, achieving Tier 3 levels as an average across
the light-duty fleet will require fleet wide reductions of
approximately 80%. This will require significant reductions from all
light duty vehicles, with the result that some models and types of
vehicles will be at most somewhat above the Tier 3 level, and all other
models will be at or somewhat below Tier 3 levels. Achieving these
reductions presents a major technology challenge. The required
reductions are of a magnitude that EPA expects manufacturers to employ
advances in technology in all of the relevant areas of emissions
control--reducing engine-out emissions, reducing the time to catalyst
lightoff, improving exhaust catalyst durability at 120,000 or 150,000
miles and improving efficiency of fully warmed up exhaust catalysts.
All of these areas of emissions control need to be improved, and
gasoline sulfur reduction to a 10 ppm average is a critical part of
achieving Tier 3 levels through these emissions control technology
improvements.
    The use of 10 ppm average sulfur fuel is an essential part of
achieving Tier 3 levels while applying an array of advancements in
emissions control technology to the light-duty fleet. The testing of
Tier 2 and Tier 3 type technology vehicles, as well as other
information, shows that sulfur has a very large impact on the
effectiveness of the control technologies expected to be used in Tier 3
vehicles. Without the reduction in sulfur to a 10 ppm average, the
major technology improvements projected under Tier 3 would only result
in a limited portion of the emissions reductions needed to achieve Tier
3 levels. For example, without the reduction in sulfur from a 30 ppm to
10 ppm average, the technology improvements would not come close to
achieving Tier 3 levels. In some cases this may result in the same
effectiveness as the current Tier 2 technology and achieve only
approximately Tier 2 levels of exhaust emissions control.
    Achieving Tier 3 levels without a reduction in sulfur to 10 ppm
levels would only be possible if there were technology improvements
significantly above and beyond those discussed above. Theoretically,
without reducing sulfur levels to 10 ppm average, emissions control
technology improvements would need to provide upwards of twice as much,
and in some cases significantly more than twice as much, emissions
control effectiveness as the Tier 3 technology improvements discussed
above in Section IV.A.6.d. EPA has not identified technology
improvements that could provide such a large additional increase in
emissions control effectiveness, across the light-duty fleet, above and
beyond that provided by the major improvements in technology discussed
above, without any additional gasoline reductions in gasoline sulfur
content. The impact of sulfur reduction on the effectiveness of the
available technology improvements plays such a large role in achieving
the Tier 3 levels that there would be no reasonable basis to expect
that technology would be available, at the 30 ppm sulfur level, to fill
the emission control gap left from no sulfur reduction, and achieve the
very significant fleetwide reductions needed to meet the Tier 3 fleet
average standards. In effect reducing sulfur from

30 ppm to 10 ppm has such a large impact on the ability of the
technology improvements to achieve Tier 3 emissions levels that absent
these sulfur reductions there is not a suite of technology advancements
available to fill the resulting gap in emissions reductions. We cannot
identify a technology path for vehicles that would achieve the Tier 3
Bin 30 average standard, across the fleet, with sulfur at 30 ppm
levels, and as a result Tier 3 levels would not be technically feasible
and achievable.
    This analysis also applies to gasoline sulfur levels between 10 and
30 ppm, e.g., 20 ppm. The Tier 3 required emissions reductions are so
large and widespread across the fleet, and the technology challenges
are sufficiently high, especially for heavier vehicles, that the large
increase in emissions that would occur from a higher average sulfur
level compared to a 10 ppm average would lead to an inability for
vehicle technologies to widely achieve Tier 3 levels as a fleet wide
average in order to meet the Bin 30 fleet average standard.
    EPA acknowledges that some models in the light-duty fleet, when
viewed in isolation, may be able to achieve Tier 3 levels at current
sulfur levels of 30 ppm average. Under the Tier 3 fleet average
standards, it is not sufficient for one or a few of a manufacturer's
vehicle models to meet Tier 3 levels because the manufacturer's light-
duty vehicle fleet as a whole must achieve the Tier 3 30 mg/mi exhaust
emissions standard as a fleet-wide average. As discussed above, all
vehicle models will need to achieve further reductions and be either
below or no more than somewhat above Tier 3 levels to achieve the Tier
3 standard as a fleet wide average. Absent the reductions in sulfur
levels to 10 ppm average, this is not achievable from a technology
perspective.
    As discussed in Section V.B, the average 10 ppm gasoline sulfur
standard is feasible and is the level that appropriately balances costs
with the emission reductions that it provides and enables. Not only
will a 10 ppm sulfur standard enable vehicle manufacturers to certify
their entire product line of vehicles to the Tier 3 fleet average
standards, but reducing gasoline sulfur to 10 ppm will better enable
these vehicles to maintain their emission performance in-use over their
full useful life. Higher sulfur levels would make it impossible for
vehicle manufacturers to meet the Tier 3 standards, and would forego
the very large immediate reductions from the existing fleet. Reducing
the sulfur level below 10 ppm would further reduce vehicle emissions
and allow the Tier 3 vehicle standards to be achieved more easily.
However, we believe that a 10 ppm average standard is sufficient to
allow vehicles to meet the Tier 3 standards. Further, as discussed in
Sections V.B and IX.B there are significant challenges associated with
reducing sulfur below 10 ppm.
7. Other Provisions
a. Early Credits
    The California LEV III program is scheduled to begin at least two
model years earlier than the federal Tier 3 program.\322\ The Tier 3
standards begin in MY 2017 for vehicles 6,000 lbs GVWR and less, and in
MY 2018 for vehicles over 6,000 lbs GVWR. As a result, LEV III vehicles
sold in California beginning in MY 2015 will be required to meet a
lower fleet average NMOG+NOX level than the federal fleet
will be meeting at that time. In addition, the California
NMOG+NOX standards will further decline before Tier 3
begins, resulting in the gap growing between the current federal
program and LEV III.
---------------------------------------------------------------------------

    \322\ See California Low-Emission Vehicles (LEV) & GHG 2012
regulations adopted by the State of California Air Resources Board,
March 22, 2012, Resolution 12-21 incorporating by reference
Resolution 12-11, which was adopted January 26, 2012. Available at
http://www.arb.ca.gov/regact/2012/leviiighg2012/leviiighg2012.htm
(last accessed December 2, 2013).
---------------------------------------------------------------------------

    We are finalizing an early credit program that with minor revisions
is as we proposed. We have designed the early credit provisions to
accomplish three goals: (1) To encourage manufacturers to produce a
cleaner federal fleet earlier than otherwise required; (2) to provide
valuable flexibility to the manufacturers to facilitate the significant
``step down'' from the current Tier 2 Bin 5 fleet average required in
MY 2016 to the LEV III-based declining fleet average in MY 2017; and
(3) to create an overall Tier 3 program that although starts later, is
equivalent in stringency to the LEV III program such that manufacturers
will be able to produce a 50-state fleet at the earliest opportunity.
Commenters were generally supportive of or silent on the early credits
program as proposed.
    The early credit program we are finalizing includes several
distinct provisions. The first provision allows manufacturers to
generate early federal credits against the current Tier 2 Bin 5
requirement \323\ in MYs 2015 and 2016 for vehicles under 6,000 lbs
GVWR and MYs 2016 and 2017 for vehicles greater than 6,000 lbs GVWR.
Early credits will only be available to manufacturers that comply under
the primary program (declining fleet average), not the alternative
phase-in approach (Section IV.A.2.c above). In order to generate these
credits, manufacturers sum the bin specific NMOG and NOX
certification standards for each federally certified Tier 2 vehicle and
the bin NMOG+NOX standards for any vehicle certified under
the Early Tier 3 provision described below and calculate an
NMOG+NOX fleet average for the entire manufacturers fleet
sold in a model year. Credits are based on how far the fleet average is
below the existing Tier 2 Bin 5 requirement (160 mg/mi total of NMOG
and NOX). We expect that manufacturers will be able to
achieve a fleetwide average below the Tier 2 Bin 5 level by several
means, such as certifying LEV III vehicles either under Tier 2 or as
Early Tier 3 vehicles under Tier 3 (discussed in the next section) to
bin levels lower than Tier 2 Bin 5. Our analysis, presented in Section
IV.A.5 above and Chapter 1 of the RIA, shows that manufacturers could
certify many vehicles currently certified to Tier 2 Bin 5 to a lower
bin--e.g., to Tier 2 Bin 3 or Bin 4--by simply accepting a relatively
small reduction in compliance margins. Many manufacturers certify Tier
2 vehicles to Tier 2 Bin 5 but also certify the same vehicle to a
cleaner emission standard under the LEV II program (e.g. ULEV) with
only a compliance margin difference.
---------------------------------------------------------------------------

    \323\ Tier 2 standards are not set in the form of
NMOG+NOX. The equivalent Tier 2 Bin 5 fleet average in
NMOG+NOX terms is equal to 160 mg/mi (90 mg/mi NMOG + 70
mg/mi NOX).
---------------------------------------------------------------------------

    We believe that the early credit provision will help us realize
both our first and second goals presented above. For example, a
manufacturer certifying their federal fleet to Tier 2 Bin 4 will earn
50 mg/mi of NMOG+NOX credits per vehicle (i.e., 160 mg/mi
minus 110 mg/mi), which we believe will encourage manufacturers to
certify a cleaner federal fleet and provide a reasonable opportunity
for credit generation to facilitate the ``step down'' in stringency.
    At the same time, if we allowed manufacturers to generate excessive
early credits, manufacturers might thereby delay their compliance with
the Tier 3 program, and thus the harmonization with LEV III, for
several years. This would be in direct conflict with our third goal of
creating a program of equal stringency to the California program as
early as possible. In order to address this concern, we proposed and
are finalizing a provision limiting the application of the early Tier 3
credits to the following conditions:
     Early Tier 3 credits generated as described above could be
used without limitation in MY 2017 on the portion of

the fleet entering the Tier 3 program in that MY.
     Credits used for compliance in MY 2018 and beyond will be
capped at an amount equal to the lesser of the manufacturer's federal
credits as calculated above or the manufacturer's LEV III credits
scaled up by the ratio of 50-state sales to California and LEV III
required states sales. This limitation accounts for the fact that some
LEV III credits may have begun to expire and will no longer be eligible
as a basis for Tier 3 early credits.
    By capping the available federal Tier 3 early credits, we believe
that the two programs, LEV III and Tier 3 will be at parity in terms of
relative stringency starting in MY 2018. In addition, because the
number of Tier 3 early credits that can be used is based on the number
of LEV III credits that the manufacturer has generated, there may be
additional motivation for manufacturers to over-perform in California
during the initial model years, accelerating emission reduction
benefits.
    Finally, we are adopting, as proposed, a limitation on the life of
Tier 3 early credits to 5 years, with no discounting, consistent with
the California LEV III program.
b. Early Tier 3 Compliance
    We are finalizing, as proposed, the requirement that manufacturers
begin the Tier 3 program in MY 2017 for vehicles up to 6,000 lbs GVWR
and MY 2018 for vehicles above 6,000 lbs GVWR under the primary phase-
in. The only proposed compliance approach available prior to MY 2017
was for manufacturers to continue to certify vehicles to the existing
Tier 2 standards with the opportunity to earn early credits (see
previous section) that could be used in MY 2017 and later.
    Several auto industry commenters suggested additional provisions
that could facilitate earlier harmonization between Tier 3 and LEV III
and streamlining of development and certification of vehicle models.
Specifically, these commenters requested the ability to have vehicles
certified to the Tier 3 standards in MYs 2015 and 2016. They commented
that this would allow them to develop, certify and sell a vehicle model
for all 50 states, reducing the complexity of potentially different
federal and California requirements in MYs 2015 and 2016. Additionally,
commenters noted that the Tier 3 program provides more flexibility in
the certification bin structure compared with the existing Tier 2,
providing them additional opportunities to generate early credits.
    To address this concern, we are finalizing a provision to allow
manufacturers to certify to Tier 3 standards starting in MY 2015 as
``Early Tier 3'' vehicles. Manufacturers will have the option to
certify their vehicle models to meet the Tier 3 emission requirements
in MY 2015 and 2016 for all LDVs, LDTs, and MDPVs, which would have
been required to begin in MY 2017 under the primary program. As an
example, a manufacturer choosing to certify a vehicle as Early Tier 3
can bring the same vehicle models certified to LEV III standards \324\
in MY 2015 or 2016 into the Early Tier 3 program by meeting all the
same requirements under the primary Tier 3 schedule. There would not be
a Tier 3 fleet average requirement for FTP or SFTP in MY 2015 or 2016
(and 2017 for vehicles over 6,000 lbs GVWR and up to 8,500 and MDPVs)
if all the same vehicle models certified to LEV III are also certified
as the Early Tier 3 vehicles meeting the same LEV III emission
standards and also the Tier 3 additional requirements (high altitude,
and cold CO and hydrocarbons). These Early Tier 3 vehicles would
replace any Tier 2 offering of the vehicle model consistent with the
LEV III offering replacing the LEV II models. If a manufacturer chooses
to certify only a portion of their LEV III vehicle models as Early Tier
3 vehicles in a given MY, they will be required to meet the LEV III
fleet average requirements in that MY for those models certified as
Early Tier 3 vehicles. All vehicles models not certified as Early Tier
3 vehicles must meet all Tier 2 requirements.
---------------------------------------------------------------------------

    \324\ Including LEV III SFTP requirements.
---------------------------------------------------------------------------

c. Useful Life
    The ``useful life'' of a vehicle is the period of time, in terms of
years and miles, during which a manufacturer is responsible for the
vehicle's emissions performance. For the Tier 3 program, we are
finalizing several changes to the existing useful life provisions that
are appropriate to the new Tier 3 standards described above.
    The auto manufacturing industry has uniformly expressed the desire
to produce and sell a single national vehicle fleet, including a
general ability and willingness of the industry to certify their
vehicles to a 150,000 mile, 15 year full useful life, as required by
the LEV III program. However, the CAA, written at a time when vehicles
did not last as long as they do today, precludes EPA from requiring a
useful life value longer than 120,000 miles (and 10 or 11 years,
depending on vehicle category and weight) for lighter light-duty
vehicles (LDVs and LDTs up to 3,750 lbs loaded vehicle weight (LVW) and
up to 6,000 lbs GVWR (i.e., LDT1s)).
    For heavier light-duty vehicles (i.e., LDT2s, 3s, 4s, as well as
MDPVs, representing a large fraction of the light-duty fleet), this
statutory restriction does not apply, and we are finalizing a 150,000
mile, 15 year useful life value, as proposed. For the lighter vehicles,
we are continuing to apply the 120,000 mile (and 10 or 11 year, as
applicable) useful life requirement from the Tier 2 program, also as
proposed. For these lighter vehicles, manufacturers are allowed to
choose to certify to either useful life value in complying with the
fleet average.\325\ In order for the Tier 3 NMOG+NOX
standards to represent the same level of stringency regardless of which
useful life value manufacturers choose, we proposed and are finalizing
proportionally lower numerical values (85 percent of the
NMOG+NOX 150,000 mile standards based on a data analysis in
Chapter 1 of the RIA) for the declining fleet average FTP
NMOG+NOX standards when a manufacturer chooses the 120,000
mile useful life. A manufacturer choosing the 120,000 mile useful life
for any vehicle must maintain separate 120,000 mile and 150,000 mile
useful life fleet averages for purposes of FTP NMOG+NOX
fleet average compliance. Credits generated towards the required fleet
averages are not transferable between the two useful life fleet
averages.
---------------------------------------------------------------------------

    \325\ CARB has stated that they do not expect to accept vehicles
certified under the federal Tier 3 program to a 120,000 mile useful
life value for California certification, and thus for meeting
California's fleet average NMOG+NOX standards.
---------------------------------------------------------------------------

    We proposed that a manufacturer that certifies any vehicle model
under the 120,000 mile provision be required to certify all their LDVs
and LDT1s to the 120,000 mile useful life and associated numerically
lower FTP NMOG+NOX fleet average standard. Comments from the
auto industry expressed a concern that this approach would be
inflexible to manufacturers' needs and unnecessarily burdensome. We
have considered these comments, and we believe that the emission
benefits of Tier 3 program will not be adversely affected if
manufacturers are allowed to certify these lighter vehicles to the
120,000 mile useful life standards on a test group basis, and therefore
we are finalizing this approach. Standards for all other pollutants
\326\ and all other test cycles such as SFTP remain the same regardless
of whether manufacturers

choose the 120,000 mile or the 150,000 mile useful life periods.
---------------------------------------------------------------------------

    \326\ PM, CO, and HCHO.
---------------------------------------------------------------------------

    For emission standards other than PM standards (e.g.,
NMOG+NOX standards), as proposed, manufacturers will be
required to certify all vehicles to the 150,000 mile useful life
beginning with the first model year that a vehicle model is certified
to the FTP NMOG+NOX Bin 70 or lower (other than vehicles not
yet required to meet a 150,000 mile useful life during the program
phase in, and vehicles for which a manufacturer has the option and
chooses to apply the 120,000 mile useful life value). This useful life
requirement will apply as early as MY 2017. Beginning in MY 2020, all
vehicles will need to certify to the 150,000 mile useful life for all
emissions, regardless of NMOG+NOX certification bin, unless
they are eligible for, and the manufacturer has chosen the 120,000 mile
useful life and associated standards. (Note that the timing of the
requirement to certify on the new test fuel follows the same approach
as for the useful life requirement for emission standards other than PM
standards (i.e., based on the first year a model is certified to FTP
NMOG+NOX Bin 70 or below) as described in the next section.)
For FTP and SFTP PM useful life requirements, manufacturers will be
required to certify to 150,000 mile useful life for PM all vehicles
that are included in the manufacturer's phase-in percentage meeting the
new PM standards (other than eligible vehicles for which a manufacturer
chooses to apply the 120,000 miles useful life value).
d. Test Fuels for Exhaust Criteria Emissions Standards
    We recognize that test fuels are an important element of a national
program. Vehicle manufacturers have emphasized in their comments the
desire to reduce their test burdens by producing one vehicle that is
tested on a single test procedure and on a single test fuel and that
meets both California and federal requirements. Although we have been
able to reasonably align the Tier 3 program with the LEV III program in
most key respects, we recognize that the Tier 3 and LEV III test fuels
are different, and that there may still exist some differences in
emissions performance between vehicles tested on the two fuels. The
largest difference between the two fuels is the Reid Vapor Pressure
(RVP), and other differences in distillation properties and aromatic
levels also exist (largely related to differences in actual in-use fuel
nationally and in California). We are finalizing as proposed the
requirement that manufacturers certify vehicles on the new Tier 3 E10
test fuels \327\ beginning with the first model year that a vehicle
model is certified to the FTP NMOG+NOX Bin 70 or lower.\328\
This requirement may apply as early as MY 2017 for vehicles up to 6000
lbs GVWR and MY 2018 for vehicles greater than 6000 lbs GVWR.\329\ This
requirement also applies to vehicles certified at Bin 70 and lower that
are brought into the Tier 3 program under the Early Tier 3 option
described in IV.A.7.b above, with the exception of the specific
provision allowing the use of LEV III fuels discussed below. Beginning
in MY 2020, all gasoline-fueled models will need to certify on the Tier
3 test fuels for all exhaust emission requirements, regardless of their
certification bin.\330\ As discussed in Section IV.A.7.c above,
manufacturers must also meet the 150,000 mile useful life requirements
for NMOG+NOX standards for these same vehicles as they are
certified to Bin 70 and lower.
---------------------------------------------------------------------------

    \327\ This includes fuels used for cold temperature and high
altitude testing and durability requirements. See Section IV.F
below.
    \328\ The lower Bins are Bin 0, Bin 20, Bin 30 and Bin 50.
    \329\ Vehicles above 6000 lb GVWR choosing the alternative
phase-in schedules described in Section IV.A.2.c above generally
would begin using the Tier 3 test fuels for MY2019.
    \330\ Diesel fueled and alternative fueled vehicles will
continue to test on the fuels used under the Tier 2 program except
for E85 fueled vehicles, for which we are finalizing new test fuel
specifications (see Section IV.F below).
---------------------------------------------------------------------------

    During the transition period from Tier 2 fuel to the new Tier 3 and
LEV III E10 fuels, manufacturers have indicated that they face a
substantial workload challenge of developing and certifying each
vehicle model to the two new fuels simultaneously. We recognize this
transitional challenge and are including an additional option. We are
finalizing as proposed an option that vehicles certified in MYs 2015
through 2019 to California LEV III standards using California LEV III
E10 certification test fuels and test procedures can be used for
certifying to EPA Tier 2 or Tier 3 exhaust emission standards,
including PM. A manufacturer may submit LEV III test data on vehicles
tested using the new LEV III E10 fuels for Tier 2 or Tier 3
certifications. Consistent with existing Tier 2 policy, EPA may test
vehicles certified to Tier 2 standards using LEV III test results on
Tier 2 fuel for confirmatory or in-use exhaust testing. For vehicles
certified in MY 2017 through 2019 to Tier 3 standards using LEV III E10
fuels, EPA will only use LEV III E10 fuels for confirmatory and in-use
testing (except for high altitude or cold CO and hydrocarbons testing,
as described below). Vehicles certified to the provisions of Early Tier
3 (Section IV.A.7.b above) will be treated the same as Tier 3 vehicles
certified in MY 2017. For example, for MY 2015 and 2016, EPA will
consider Early Tier 3 vehicles to be part of the Tier 3 program for
purposes of fuel-related testing obligations. We will not accept test
results using LEV II fuels for Tier 3 vehicle certification, including
Early Tier 3 certifications, with the exception of the PZEV exhaust
carry-over provision described below.
    California does not have fuel specifications for high altitude
testing or cold CO and hydrocarbon testing. For this reason, we are
finalizing that for vehicles that manufacturers choose to certify using
LEV III fuel and test procedures, manufacturers must use program-
specific federal test fuels to comply with these federal-only
requirements (i.e. Tier 2 vehicles will use Tier 2 fuel and Tier 3
vehicles will use Tier 3 fuel). Similarly, high altitude and cold CO
and hydrocarbon confirmatory and in-use testing for these vehicles will
be performed on the federal fuel that the manufacturer is required to
use at certification as specified above regardless of whether LEV III
or federal fuel is used for other testing.
    We proposed the requirement that after MY 2019, all Tier 3
certification, confirmatory and in-use emission testing be required to
use only the proposed Tier 3 E15 test fuel because it was believed to
be a worst case fuel for emissions. Because we are finalizing Tier 3
E10 test fuels which are very similar as explained above to LEV III E10
test fuels, and not considered a worst case fuel, we are not finalizing
the requirement for all testing to be performed on Tier 3 E10 test
fuel. Instead, for certifications after MY 2019, EPA will continue to
allow LEV III test results to be submitted for certification to Tier 3
standards, consistent with protocol under the Tier 2 program. However,
if a manufacturer chooses to submit certification results for
compliance with Tier 3 standards using the LEV III test fuel, then for
confirmatory and in-use testing we will hold vehicles to the Tier 3
standards while using the Tier 3 fuel in addition to the LEV III test
fuel; we will not allow new or carry-over certifications using LEV II
or Tier 2 certification test fuels after MY 2019. CARB has indicated
that they will accept Tier 3 test data (on federal certification test
fuels) to obtain a California certificate as early as MY 2015. In this
manner manufacturers should be able to avoid compliance testing on more
than one fuel, since vehicles certified to Interim or Final

Tier 3 status using federal certification test fuels could also obtain
LEV III certification.
    Auto industry commenters noted that the LEV III program provides an
allowance for manufacturers to carry over PZEV-certified vehicle
exhaust data \331\ from the LEV II program into LEV III compliance in
MY 2015 through MY 2019. Thus, CARB allows these PZEV vehicles to use
emission testing results using LEV II fuel (i.e. California Phase II
test fuel) to meet the LEV III obligations. The commenters suggested
that EPA allow manufacturers to carry over such PZEV 150,000 mile
useful life exhaust emission data to meet the Tier 3 standards. We
agree that this approach is appropriate during the transition, and we
are finalizing this provision for MY 2015 through MY 2019, including
allowing Early Tier 3 compliance at the Bin 30 level as a combined
NMOG+NOX standard. EPA will hold vehicles certified using
this provision to the Tier 3 emission requirements when they are tested
on the LEV II fuel for confirmatory and in-use. Compliance testing of
these vehicles for all other Tier 3 obligations (i.e., high-altitude
testing and Cold CO and hydrocarbons testing) must be performed using
Tier 3 fuel, and these vehicles will be required to meet the Tier 3
standards for Bin 30.
---------------------------------------------------------------------------

    \331\ California's PZEV exhaust standards are the same as their
SULEV standards and the Tier 3 Bin 30, and are certified to a
150,000 mile useful life.
---------------------------------------------------------------------------

e. High Altitude Requirements
    FTP emission standards are historically designed to be applicable
at all altitudes. Under Tier 2, the same FTP emission bin standards
applied to vehicles tested at both low and high-altitude. However,
fundamental physical challenges exist at high altitude resulting in
typically higher emissions during cold starts compared with starts at
lower altitudes (i.e., sea level), and these challenges become more
pronounced as emission standards become more stringent. This expected
increase in emissions is primarily due to the lower air density at
higher altitudes. Due to the lower air density, the needed volume of
the hot combustion exhaust required to quickly heat the catalyst in the
first minute after a cold start is reduced. As a result, catalyst
light-off is delayed and cold start emissions can increase. Vehicles
under the Tier 2 program typically have had sufficient compliance
margins to absorb this increase in emissions during testing under high-
altitude conditions. However, given the extremely low standards we are
finalizing in Tier 3, manufacturers will have less compliance margin
with which to address the issue.
    Under the Tier 3 program, we expect that the emission control
technologies selected for low altitude performance will also provide
very significant emission control at high altitude.\332\ However, as
explained above, unique emission challenges exist with operation at
higher altitude, often requiring manufacturers to design their emission
controls specifically for higher altitude.
---------------------------------------------------------------------------

    \332\ High-altitude conditions means a test altitude of 1,620
meters (5,315 feet). Low altitude conditions means a test altitude
less than 549 meters (1,800 feet).
---------------------------------------------------------------------------

    We do not believe that the impact of the fairly small fraction of
overall U.S. driving that occurs in high altitude locations warrants a
requirement for additional technologies to be applied specifically for
high-altitude conditions. To avoid requiring manufacturers to use
special high-altitude emission control technologies, we are allowing
manufacturers limited relief for certification testing at high
altitude, as proposed. Specifically, for sea-level certifications to
Tier 3 Bins 20, 30, and 50, a manufacturer could comply with the next
less-stringent bin for testing at high altitude. For example, a
manufacturer can certify to Bin 50 for testing at high altitude versus
Bin 30 at sea level). For vehicles certified at sea level to Bins 70
and 125, manufacturers can comply with standards 35 mg/mi higher (e.g.,
105 mg/mi and 160 mg/mi, respectively. We are providing no high
altitude relief for vehicles certified to Bin 160. This high altitude
relief provision applies to all Final Tier 3 vehicles for the duration
of the Tier 3 program.
    For intermediate altitudes that fall between the specified low and
high altitude test conditions, the emission performance should continue
to be representative of the controls implemented to meet standards at
the required altitude test conditions, consistent with Tier 2 protocol.
Any deviation in the use of these controls at the intermediate
altitudes may be considered an AECD that must be reported by the
manufacturer and justified as not being a defeat device.\333\
---------------------------------------------------------------------------

    \333\ Sec.  86.1809-12 Prohibition of defeat devices
---------------------------------------------------------------------------

    Table IV-9 presents the Tier 3 high altitude standards.

               Table IV-9--Tier 3 High Altitude Standards
------------------------------------------------------------------------
                                           Sea level FTP   Altitude FTP
                   Bin                     standard (mg/   standard (mg/
                                           mi NMOG+NOX)    mi NMOG+NOX)
------------------------------------------------------------------------
Bin 160.................................             160             160
Bin 125.................................             125             160
Bin 70..................................              70             105
Bin 50..................................              50              70
Bin 30..................................              30              50
Bin 20..................................              20              30
------------------------------------------------------------------------

f. Highway Test Standards
    Sustained high-speed operation can result in NOX
emissions that may not be represented on either the FTP or SFTP cycles.
Although we are not aware of any serious issues with this mode of
operation with current Tier 2 vehicles, we are interested in preventing
increases in these NOX emissions as manufacturers develop
new or improved engine and emission control technologies.
    For this reason, we are finalizing, as proposed, a provision that
the Tier 3 FTP NMOG+NOX standards above also apply on the
Highway Fuel Economy Test (HFET), which is performed as a part of GHG
and Fuel Economy compliance testing. Thus, the Tier 3 FTP
NMOG+NOX standard for the bin at which a manufacturer has
chosen to certify a vehicle will also apply on the HFET test. For
example, if a manufacturer certifies a vehicle to Bin 70, the vehicle's
NMOG+NOX performance over the HFET could not exceed 70 mg/
mi. Manufacturers will simply need to ensure that the same emission
control strategies implemented for the FTP and SFTP cycles are also
effective during the highway test cycle. We believe that this
requirement will not require manufacturers to take any unique
technological action, will not add technology costs, and will not add
significantly to the certification burden.
g. Interim 4,000 Mile SFTP Standards
    During the period of the declining NMOG+NOX standards,
we are finalizing the proposed requirement that interim Tier 3 vehicles
meet 4,000 mile SFTP standards, consistent with the existing Tier 2 and
LEV II program requirements. The 4,000 mile standards apply to each
vehicle model individually and to each component of the SFTP composite
cycle. This approach is designed to prevent excessive emission levels
from individual vehicle models being masked by the averaging of the
manufacturer's fleet emissions. Similarly, this approach also prevents
poor performance on a

single cycle of the SFTP. We believe it is appropriate to require any
individual Interim Tier 3 vehicle to at a minimum meet the existing
requirements under the Tier 2 and LEV II programs. Table IV-10 below
presents the 4,000 mile SFTP standards for interim Tier 3 vehicles.

                   Table IV-10--4,000 Mile SFTP Exhaust Standards for Interim Tier 3 Vehicles
                                                  [grams/mile]
----------------------------------------------------------------------------------------------------------------
                Vehicle category                   US06 NMOG+NOX      US06 CO      SC03 NMOG+NOX      SC03 CO
----------------------------------------------------------------------------------------------------------------
LDV/LDT1........................................            0.14             8.0            0.20             2.7
LDT2............................................            0.25            10.5            0.27             3.5
LDT3............................................            0.4             10.5            0.31             3.5
LDT4............................................            0.6             11.8            0.44             4.0
----------------------------------------------------------------------------------------------------------------

    We believe that vehicles considered to be Final Tier 3 vehicles
(i.e., they meet the Tier 3 PM requirements, specifically the stringent
SFTP PM standards) will have sufficiently robust designs that the 4,000
mile SFTP standards will no longer be necessary and so will not apply
to those vehicles. Additionally, once the program reaches the fully
phased-in fleet average composite standard of 50 mg/mi in 2025, high
SFTP emissions even on a limited portion of a manufacturer's fleet
should be effectively mitigated, and the 4,000 mile SFTP standards will
no longer apply.
h. Phase-In Schedule
    As proposed, the major provisions of the Tier 3 program phase in
based on model year and on the emission levels to which manufacturers
certify their vehicles. As described in Section IV.A.3, under the Tier
3 program, manufacturers are required to certify each vehicle model to
an FTP bin, which is then used to calculate the NMOG+NOX
fleet average of all of its Tier 3 vehicles. Manufacturers must also
determine the SFTP levels of each model and calculate the
NMOG+NOX fleet average for the SFTP requirements as
described in Section IV.A.4. These separate FTP and SFTP fleet average
calculations satisfy one aspect of certification under the Tier 3
program, specifically the standards associated with each model year.
    As described in Sections IV.A.7.c and IV.A.7.d above, the longer
(150,000 mile) useful life value, as applicable, and the new Tier 3
test fuel for exhaust testing will be implemented as manufacturers
certify vehicles to more stringent NMOG+NOX standards, with
the threshold to implement both of these provisions being Bin 70.
Beginning in MY 2017, any vehicle certified to Bin 70 or lower will be
required to be certified on Tier 3 test fuel. In addition, any vehicle
certified to Bin 70 or lower that is required to meet the longer
150,000 mile useful life will be required to do so at that point.
Independent of the Tier 3 test fuel phase in schedule, the 150,000 mile
useful life for PM standards will be required when the vehicle is
certified to the new Tier 3 PM standards as described below in the PM
phase-in schedules. Beginning in MY 2020, all gasoline-fueled vehicles
will be required to be certified for exhaust emissions on the Tier 3
test fuel, regardless of their certification bin or applicable useful
life.
    Manufacturers must also comply with more stringent PM standards on
a percent phase-in schedule. Compliance with the PM standards, which is
consistent with the CARB LEV III program, is independent of the
NMOG+NOX fleet average requirements described above. The PM
emission standards for FTP and SFTP described in Section IV.A.3 and 4
respectively will be implemented as a percent phase-in requirement as
described below under a primary phase-in schedule or under an optional
phase-in schedule.
    Vehicle models that a manufacturer certifies to a Tier 3
NMOG+NOX bin, that meet the requirements of the PM phase-in
schedule, and that comply with the other Tier 3 requirements (i.e.,
150,000 mile useful life and Tier 3 test fuel, as applicable) will be
considered ``Final Tier 3'' compliant vehicles. All other vehicles
certified to Tier 3 bins but not yet meeting the PM and other Tier 3
requirements will be considered ``Interim Tier 3'' compliant vehicles.
At the completion of the percent phase-in period for PM (2021 for the
primary PM phase-in schedule and 2022 for the optional PM phase-in
schedule, as described below), 100 percent of vehicles will need to
meet all of the Tier 3 requirements and will be considered Final Tier 3
vehicles.
    As proposed, for the PM requirements, each model year manufacturers
must meet either the primary PM percent phase-in or the optional PM
phase-in as described in the following subsections. The primary percent
PM phase-in schedule is composed of fixed annual minimum phase-in
percentages that we expect most manufacturers to choose in order to
comply with the Tier 3 requirements. The optional PM phase-in schedule
provides additional flexibility for manufacturers with too few product
offerings to allow for a sufficiently gradual transition into the Final
Tier 3 requirements, as described below. In either case, Interim Tier 3
vehicles not yet meeting the Tier 3 PM standards must at a minimum meet
the Tier 2 PM full useful life FTP PM standard of 10 mg/mi and the SFTP
PM weighted composite standard of 70 mg/mi.
i. Primary PM Percent Phase-In Schedule
    It is important to note that the percent phase-in of the new Tier 3
PM standards and the declining fleet average NMOG+NOX
standards that we are finalizing are separate and independent elements
of the Tier 3 program. ``Phase-in'' in the context of Tier 3 PM
standards means the fraction of a manufacturer's fleet that is required
to meet the new Tier 3 PM standards in a given model year. We expect
that manufacturer fleets may consist of a mix of vehicle models
certified to Tier 2, LEV II, LEV III and Tier 3 standards throughout
the percent phase-in period.
    As discussed above, vehicles originally certified to Tier 2, LEV
II, and LEV III may be carried over into the Tier 3 program as Interim
Tier 3 vehicles. A vehicle will be considered a Final Tier 3 vehicle
when it is certified to one of the Tier 3 bins, meets the new Tier 3 PM
standards for FTP (3mg/mi) and US06 (10 or 6 mg/mi), certifies to the