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2009 Fuel Economy Guide and

October 24, 2008 - 4:00am


With energy costs looming as winter approaches, saving money is on everyone's minds these days. Fortunately, improving your vehicle's fuel economy is both economically and environmentally smart.  In the winter, one of the easiest ways to decrease gasoline consumption is to warm up your engine for no more than 30 seconds, as Elizabeth pointed out last week. Driving conservatively and buying a fuel efficient car can make even more of an impact.

The 2009 Fuel Economy Guide, released on October 15, can help you choose the most fuel efficient car for your needs, both new and used.  Whether you are in the market for a compact car or minivan, the Guide provides the miles per gallon and annual fuel cost for every passenger vehicle available this year. The Guide’s Web site,, and its companion mobile site, provide a number of special features in addition to the basic statistics.

To talk about the new DOE / EPA Fuel Economy Guide and how drivers can decrease the amount they pay at the pump, I interviewed Dr. David Greene, a national expert on fuel economy at DOE's Oak Ridge National Laboratory.

Shannon: Why should the average person care about the Fuel Economy Guide?

David: I think the average person should care about the Fuel Economy Guide and for the same reason they care about fuel economy. First and foremost, fuel economy saves them money. The typical car in the United States, even at three dollars a gallon of gasoline, will use about $2000 worth of gasoline each year. And by choosing carefully, when you purchase a new or used car, you can save a very large fraction of that. Second, for most of us, our automobiles and trucks are the largest component of our carbon footprint. A typical car emits about 8 tons of carbon dioxide every year. So there again, we have a way of affecting how much damage our vehicle does to the climate. And finally, there's the problem of our dependence on petroleum. And I don't mean just imported petroleum or petroleum from certain countries. But I mean our overall economic and strategic dependence on petroleum. By our estimates, the economic damage from petroleum dependence this year alone is approximately three-quarters of a trillion dollars.


Shannon: Wow.

David: So that's not entirely responsible for the economic mess we're in, but it's certainly a contributing factor.


Shannon: How do you calculate fuel economy?

David: Well, fuel economy is calculated by the Environmental Protection Agency, and especially by the automobile manufacturers, on what's called a chassis dynamometer. So it's a device that sits in a very large laboratory. A car is driven up onto it, [with] the front or the rear wheels, whichever [are] the driving wheels, on drive rollers, and the car is driven over a test cycle.  If you go to, you can see not only choices of these test cycles, but you can see video of the cars actually being tested on them.  Now, even though the cars are driven in a laboratory, adjustments are made to account for things such as aerodynamic drag and tire rolling resistance, probably to get a better sense of real-world fuel economy. Vehicles are tested on two cycles – a city cycle and a highway cycle. In the future, cars will be tested on 5 cycles, reflecting different conditions, such as cold, climate conditions, aggressive driving and use of air conditioners. So the EPA has come up with a new ratings system that is based on these 5 cycles and will hopefully give a more realistic estimate of what people get in the real world. Now, once these test cycle numbers are calculated, they are further adjusted based on statistical experience of what real people actually get on the road to try and better estimate on average what a real driver is going to get using that vehicle. There's a downward adjustment that’s made before the numbers are put into the gas mileage guide or put on the Web site.

Shannon: And when do they expect to start using that new ratings system?

David: Well, we use the new ratings system now, but most of the cars are still tested on the two-cycle test.

Shannon: So it's the new ratings system, but still on the old cycle?

David: Right. And the manufacturers have a few years in which to transition to the new 5-cycle tests.


Shannon: And will everybody achieve the same fuel economy that's written on the sticker?

David: No. Fuel economy is not a fixed number, like the weight of a car or the horsepower.  The fuel economy depends on where you drive, how you drive.  It depends on the temperature when you drive, it depends on whether you take short trips or long trips, it depends on traffic conditions, it depends on many, many factors.  And so, it's a variable.  And you have some control over your car's fuel economy, but [there's] also the external conditions like temperature that you can't control.  Or lengths of trips you need to take.  Well, you may be able to do something about that by combining trips.  But by and large, there are many factors, like traffic conditions, that determine fuel economy that you don’t control.  And so different people are going to get a different fuel economy experience for the same car.

Shannon: What do the top fuel efficient vehicles have in common?  What makes them so fuel efficient?  [Note: The most and least fuel efficient vehicles are listed on at 2009 Most and Least Fuel Efficient Passenger Cars and 2009 Most and Least Fuel Efficient Trucks,Vans and SUVs.]

David: Well, I think, number one is good engineering.  And use of technologies that are available to maximize fuel economy.  You will find a large number of hybrid vehicles and you will find a disproportionate number of diesel vehicles on the top fuel economy list.  But you’ll also find a lot of gasoline-powered vehicles that are simply designed and built to achieve high fuel economy. 

Shannon: The diesel vehicles are pretty new, right?

David: Yes.  Up until the past couple of years, diesel vehicles were not able to meet our air pollutant emissions standards.  And only in recent years have the diesel manufacturers developed the technology to make those vehicles clean enough to meet emissions standards.  And so now that that technology is in place, things like particulate filters that clean the particles from diesel vehicles, and lean NOx catalystics or various kinds of nitrogen oxide (NOx) control devices, reduce the smog-forming pollutants from diesel vehicles to levels that are as good as gasoline vehicles.  So now that those vehicles have that advanced pollution control technology, manufacturers are beginning to introduce them into the market to see whether customers like them.

Shannon: And are they expecting to start combining some of these technologies together to have even higher fuel efficiency?

David: Well, I don't think that we will see very soon, diesel hybrids, for example.  I think we'll see many more gasoline hybrids and we'll see some more diesel vehicles. Especially with diesel vehicles in the luxury car classes and the larger truck classes, where the diesel engine's torque, which is really good for towing, is especially valuable. We may see some plug-in hybrid vehicles coming out in the next few years.  That's dependent on continued battery progress.  It depends on that, but I think manufacturers would very much like to introduce these vehicles. And I think the first ones we'll see will not have long electric ranges, but will allow you to plug the vehicle in and take some energy from the electricity grid, rather than having to buy all of your energy in the form of gasoline.

Shannon: What unique features does offer drivers?

David: The number one feature I think we offer is our Your MPG feature, where now about 25,000 motorists from around the country have told us what fuel economy they get with their car.  So you can compare the experience of real people with the official government ratings.  And I think that's extremely valuable to people for having a basis for comparison.  You can also see how much real people's experience varies and that will give you a sense of what your MPG might be.  There are a number of other features that people find useful.  Our fuel economics feature, for example, doesn't just tell you, 'you get 25 miles per gallon,' it tells you how much it will cost you to drive this car 25 miles.  What is your annual fuel bill likely to be?  Those kinds of things.  And I think we're the only place that I know of where you can get complete ratings on the greenhouse gas emissions from light duty vehicles, cars and trucks, from model year 2009, all the way back to 1985. 

Shannon: Now, obviously not everybody is in the market for a new car.  What can consumers do to improve the fuel economy of their current vehicle? 

David: Well, first of all, as I said, we have used car fuel economy ratings going back to 1985, so if you're in the market for a car, new or used, the site can help you compare.  But there are also many things that people can do in their own driving to maximize fuel economy.  Let me just mention that in our Your MPG Web site, those 25,000 people, three-quarters of them are beating their EPA ratings. So if they can do it, you can do it, probably.  And these are things like staying within the speed limit.  Speed reduces your fuel economy.  And every five miles per hour you drive above the speed limit is going to cost you seven or eight percent in your fuel economy.

Shannon: Yeah, that's significant.

David: Also, avoiding aggressive driving.  Stomping on the accelerator, passing everybody, tailgating so that you have to use your breaks excessively, failing to anticipate traffic conditions.  These kinds of things can waste an awful lot of fuel–anywhere from 5%-30%, depending on how aggressively you're driving.  So that matters as well.  And then there are the usual things you can do to keep your car properly maintained, such as ensuring your tires are properly inflated.  That not only helps your fuel economy but it makes your tires last longer and it's safer.  Getting junk out of your car that you're carrying around in the trunk or in the flat bed of your pickup truck.  These kinds of things can also help because every 100 pounds or so is going to cost you a couple percent in fuel economy. So if you've got stuff in there that you should have taken out but you're just carrying it around, you're wasting fuel.  Also, if you have a car top carrier that you’re not using, that increases the drag and you can take that off and save some fuel as well. Other things you can do include planning your travel, both to reduce the amount of travel you have to do and to make sure your car is fully warmed up as you're making many trips at once instead of a lot of small trips.  It takes actually quite a bit of energy for an engine to warm up to its proper temperature. 

Shannon: I didn’t realize how much fuel was used myself before I read about that recently.

David: So I think if you can plan a little better, then you can definitely save some fuel.  Of course, we have lists of maintenance tips and driving tips on

Shannon: Great.  Is there anything that you think people should know about the Fuel Economy Guide or that we didn't talk about?

David: Well, I think they'll find a lot more features on there than we've been able to cover.  There is everything on information from how to get your tax credit or your tax incentive for purchasing a hybrid, a diesel or an alt-fuel vehicle to links to sites that can tell you where you can buy E85 to latest news articles on fuel economy and on and on and on.  So I think people who go there will really find there's a tremendous wealth of information on the subject.

Shannon: Thank you so much!

David: You're welcome.