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  • Bridging the MPG / EPA Gap - Editor's Desk

Bridging the MPG / EPA Gap - Editor's Desk

There are things I could do that would make a huge difference in mpg during the commute.

Allyson Harwood
Sep 25, 2013
Fuel economy is a controversial topic. It seems that more often than not, the fuel economy numbers on a vehicle's window sticker are higher than in real-world driving. While that's understandable, when people see an EPA-approved fuel-economy number, they expect to get that same fuel economy. If they don't get the results they were expecting, they're going to be disappointed. If there's too much of a difference, it may change the way they think about specific automakers.
It doesn't help that most of the buying public don't know all that much about how the EPA determines the numbers that end up on the Monroney (the window sticker). If you look at the EPA's website (, the agency offers an overview of its evaluations, as well as the full text of the Code of Regulations that relates to it: 40 CFR Part 600, "Fuel Economy and Greenhouse Gas Exhaust Emissions of Motor Vehicles." It's a lot to wade through. The website also explains that the "Corporate Average Fuel Economy (CAFE) requires vehicle manufacturers to comply with the gas mileage, or fuel economy, standards set by the Department of Transportation (DOT). CAFE values are obtained using the city and highway fuel-economy test results and a weighted average of vehicle sales. Tests are conducted in a laboratory by operating vehicles on a dynamometer. The EPA administers the testing program that generates the fuel-economy data. The National Highway Traffic and Safety Administration (NHTSA), part of DOT, is authorized to assess penalties based on the information the EPA supplies and to modify the standards."
Photo 2/2   |   2012 Ford F 150 Dash Guages
Yet elsewhere on the site, the EPA states "the test data is derived from vehicle testing done at the EPA's National Vehicle and Fuel Emissions Laboratory in Ann Arbor, Michigan, and by vehicle manufacturers who submit their own test data to the EPA." So the manufacturers do their own testing, based on EPA parameters, and some testing is done in Ann Arbor. Most people who are buying a vehicle haven't read 40 CFR part 600 and presume that what the sticker says is what the vehicle will do.
However, as much as we'd like to pooh-pooh the EPA's testing regimen, that isn't fair, and unfortunately, a lot of the reason for the difference between what the sticker says and reality is lies squarely at the feet of the driver. I know this from personal experience.
When manufacturers evaluate vehicles for the EPA rating, they test them on dynamometers, which ensures the testing is done in a way that's consistent and repeatable. That means the tests can't completely account for sitting in traffic with the air conditioner on -- even though one new test does include some use of the A/C. While there are some stretches of traffic that we all know are a part of our daily lives, those are regional issues, and not necessarily fair to include in nationwide fuel-economy evaluations.
Not everyone's commute involves a lot of traffic, and A/C isn't an issue year round. Not everyone spends 80 percent of the daily drive sitting in traffic. Los Angeles traffic patterns -- and driving habits -- may be the worst of all. We sit in stop-and-go congestion for long stretches with the A/C cranking (really bad for fuel economy), and when things do finally open up, we floor it (also really bad for fuel economy). I'm guilty of this, but I don't drive that way all the time. However, I'm not surprised that I'm not getting as much range out of each tank as I should.
So what can we do? Speaking for myself, I can try to become a more well-behaved driver. There are things I choose not to do that would make a huge difference during the commute. While I already use the instantaneous fuel-economy gauge to get an idea of how the tank's mpg is faring, I could use the cruise control any time I'm driving faster than 35 mph, which is generally the minimum speed for those systems to work. I can turn off the air conditioner more often and drive at lower speeds with the windows down. I could be less aggressive when accelerating. Just because traffic has finally opened up doesn't mean I have to get to speed immediately. I could relax and it would save money in the long run. Smooth driving always helps.
While it would be nice if the EPA's testing methods were easier to understand, and most consumers aren't totally clear on how the testing works, the fuel economy listed on the window sticker isn't that far from what is possible. I think if I drove a more sensibly, I could get closer to the highway mpg number.
Maybe we as drivers could compromise and change our driving habits, and the EPA could compromise and make it easier for the public to understand how the agency gets its numbers.
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