Real World Challenges with Diesel Exhaust Fluid

Real World Diesel Exhaust Fluid Challenges

Though we’re more than halfway through 2010, it can be a challenge to find and use diesel exhaust fluid, as we found out recently during our 2010 Heavy-Duty Shootout comparison test in Michigan.

We staged all of our long-distance testing out of the Pilot Travel Center in Dexter, just west of Detroit. It’s currently the only Pilot location in the state where DEF is dispensed at a self-service pump outside next to diesel fuel pumps, instead of sold in bottles.

Pilot has been a leader rolling out DEF pumps across the country, but the DEF pump in Dexter was out of order while we were there, and Pilot staff said it had only worked sporadically since it was installed several months ago.

What’s the big deal about DEF?

On Jan. 1, tough new EPA emissions regulations required all new diesel engines to reduce nitrogen dioxide emission levels by 90 percent from 2007 and by 96 percent from 1994.

DEF Pump

NOx is a major air pollutant that contributes to smog, asthma and respiratory and heart diseases. It's a byproduct of diesel’s high combustion temperatures, which result from the high frictional heat levels created by compressing air in the cylinders to the point where it can ignite diesel fuel without a spark. DEF in diesel-powered pickup trucks uses urea selective catalytic reduction to lower the emissions.

Truck manufacturers have split into several camps over which NOx reduction method is best for their trucks. Pickup trucks that require DEF include the 2011 Ford F-Series Super Duty, powered by the all-new 6.7-liter Power Stroke V-8, and the 2011 Chevrolet Silverado and GMC Sierra HD pickups, powered by the updated 6.6-liter LML Duramax V-8. The Ram truck lineup uses two different methods to scrub NOx. Ram 2500 and 3500 pickup trucks use a urea-free NOx absorber catalyst that doesn’t require DEF, while Ram 3500, 4500 and 5500 chassis trucks use urea SCR and DEF.

Because diesel trucks that run out of DEF are no longer emissions-compliant, they are virtually immobilized when the DEF tank runs dry, even if there’s diesel fuel available to keep them trucking. Ford, GM and Chrysler have similar strategies to alert drivers when their DEF tanks have 1,000 miles or less range left, so modern diesel drivers won’t get stranded on the side of the road.

We were fortunate because all of our trucks’ DEF tanks were still more than half full. It would have been inconvenient if they needed to be refilled.

Pilot’s pump price for DEF was a reasonable $2.99 a gallon, compared with almost $32 a gallon that Consumer Reports recently paid a Mercedes-Benz dealer to refill a GL SUV. Inside the Pilot store in Dexter, a one-gallon bottle of DEF cost $5.99, though Pilot staff graciously reduced that price to $2.99 because the DEF dispenser wasn’t working.

DEF Dispenser Nozzle in Ford Super Duty DEF Tank Receiver
Photo courtesy of Diesel Power Magazine / David Kennedy

Check back August 16 for the full results of our 2010 Heavy-Duty Shootout, including the results of our first-ever DEF usage test recorded during our 300-mile fuel economy loop.


What temp is the DEF stored at in the tanks? The higher the temps the lower the shelf life is. The last diesel course I went to had a chart on the shelf life/storage temps. Could be a problem in the southern states where its hot year round.

Auto Parts stores are starting to sell it in 1 gallon jugs. $13.99 a gallon (cdn). Glad I don't need any for my current diesels, 2010 Cummins 3500 and 2007.5 Duramax 2500.

DEF sucks!!! You can get it at your local dealer anyway. :D

I love the smell of DEF in the morning.

August 16Th? Why the magic date?

Hey Mike,

Does the 6.7L diesel still go into regen mode to clean out the DPF with the new DEF added to the system?

Rob, the DEF replaces diesel fuel used in the previous generation emission system during regen. So yes it does. The gain in MPG's on the new generation diesel is partially attributed to this change. However, as noted in this article, you will pay (in the form of UREA) for buying less diesel fuel. How much overall cost savings at the pump will be determined in the months ahead.

@ Evan, Thanks that clears up an arguement I had with someone at work.

You are wrong. The DEF is used in the SCR brick to reduce NOx. It has no effect on DPF regens. A DPF regens by getting very hot, DEF does not burn and does not provide the heat needed to regen the DPF. Both the Ford and GM both regen using diesel fuel like they did before.

You will soon be able to purchase DEF at Farm equipment suppliers. As of 2011 all off road diesels have to meet the same emission standards as on road diesels. I would think you will get DEF at these stores cheaper than most other places. Except John Deere dealers as their engines are still EGR.


Thats interesting, since cat left the on road market because they didn't want to invest in cleaning up their diesels, so now they are still going to have to do it anyway? Must suck to be Cat right now

sucks to be anyone with a new diesel right now. I imagine those hunting for a diesel are now hunting for a used truck rather than those with urea and DEF.

Cummins has proven that you can build an engine that does not use DEF.
The thing that puzzles me is why the same engine in Ram's 4500 andd 5500 use DEF.
Does anyone have the answer to that?

I'm pretty sure it's because the LNT (Lean NOx Trap) system that Dodge is using on the 3500 hurts fuel economy at the higher loads. I guess they figure the trade off is worth it on the 3500, but on the 4500+ truck since you are going to be at higher loads more often, the fuel economy trade off isn't worth it.

The reason LNT hurts FE is because like a DPF you have to "regen" the LNT (called DeNOx). To DeNOx it you have to run rich briefly which obviously uses extra fuel. And higher loads create more NOx, which means you have to DeNOx it more often.

@ Lou and Tim The reason for the 45-5500s using DEF is cost. The NOX catalyst that Chrysler uses is expensive due to the metals inside. It has nothing to do with fuel efficency. I think that the better mileage claim was made up by Ford so that the added expense of this system wouldn't scare away buyers of its new money maker. The last Chrysler diesel course I went to explained all about it. And never once was mileage benefit brought up. How exactly does spraying a liquid into the exhaust help you burn less fuel. Last time I checked exhaust was BURNT FUEL. Adding a liquid to the burnt fuel(exhaust) will have no effect on the fuel going into the engine about to be burned or how effectivly and cleanly the fuel will be burned. Ford's marketing guys are earning there pay, nothing more.

I'm pretty sure FE does have something to do with it. I know for a fact the clean the LNT you have to run rich, and to run rich you either close the throttle (increase pumping losses) or injected a post injection (using extra fuel like a regen). I guess we'll have to see what happens in the shootout.

As for how DEF help you burn less fuel - obviously it doesn't directly impact the amount of fuel injected into the cylinder. It does however allow the engine to run more efficiantly because you can advance the timing which help fuel economy but also increases NOx emissions. With the DEF system though, you can have higher engine out NOx because the DEF system will reduce it. So the DEF system can and does help fuel economy in certain situations.

@ Tim I searched the Chrysler repair website and it has no info on the NOX adsorber catalyst that Chrysler uses instead of DEF other than it does have to regen but it doesn`t say how. So you could be correct there. I`m sure you know this but diesels don`t have a throttle (not counting the throttle used in EGR operation). Also, could you explain how advancing the timing helps economy? I`m having trouble wraping my head around Fords claim and no one seems to have any idea how it works, they just beleive it does. Any info you have or links would be appreciated. Thanks.

The NOX adsorber catalyst in the Rams are extremely expensive. I've heard 3-4 grand. (anyone know what they cost?)
The local dealer had them stolen from a bunch of new diesel trucks last year. I'd hate to have to replace one.
I wonder how long the emissions warranty is on one?
That is one thing a guy has to consider - is DEF going to be cheaper in the long run than having to replace a NOX adsorber catalyst .
If you live in a jurisdiction that does not check emissions or levie fines - one can just torch it off when it fails and weld in a piece of pipe - assuming the truck's computer will let it run without the catalyst.

@ Lou I have never seen or have heard of a NOx Adsorber catalyst failing since Dodge began using them in 07 and as such I have know idea what it would cost to replace one. You are likely correct when you say they are not cheap. When it comes to the theft of such things you would think that someone would obviously call the cops on the perp. Most law abiding people don't have several NOx adsorbers in thier posession.
Speaking of dealer theft guys where taking wheels and tires from our lot, so we put wheel locks on them, then they started taking tailgates, so we put locks on them, then they started taking the spares, so we put locks on them. Salesmen, being somewhat lazy, decided to keep all these locks in the glove box to cut down on the leg work. A "customer" obviously got wind of this and one morning we came to work to find missing wheels/tires/spares/tailgates with the added convenience of broken side glass. Now the locks are kept inside the building and none of our s!!t gets stolen anymore. True story.

i'm using def in a 2011 pete 389 with a 500 hp cummins. the price of the def is making it extremely hard to make any money at trucking. when will the cost of it come down to a reasonable level? i'm all for clean air, butt not if it puts me out of business.

i agree with john- the price of DEF until it gets to a pump is killer. The only one making any money is the creators of DEF fluid. Why would they want to install pumps when they can charge $18.00 a gallon on the shelf?? If the government said this had to happen in 2008 for 2011, why is it nearly 2011 and the fluid is not readily available? anyone can write me about this becaue I'm about to start a class action lawsuit.

You can get DEF at all O'Reilly Auto Parts. $4.99/gal or $11.99 for a 2.5 gal.

OK so what happens if you just put distilled water into the DEF tank? I'm thinking of buying 2011 F350 for use in Mexico & overseas (no DEF available there) and am really wondering about going with a diesel.

At least for GM, using anything but 33% Urea DEF will cause "Exhaust Fluid Quality" problems which will eventually still limit you to 55 mph for ~200 miles, then limit you to ~4 mph (yes I said 4). It will let you "limp" to get your tank drained and filled with good quality DEF.

It is getting easier and easier to find DEF, and more and more people are becoming aware of it, what it does, and who needz it.

def is dissolved urea which is a compound found in urine i could be wrong but rather then be stranded couldnt you just piss in the def tank.

Use up 5 gallons of def in about 1000 miles.

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