Gas Mileage Calculations: Why MPG Numbers Really Matter

Gas mileage calculations have recently changed to more accurately reflect real-world mpg. Here’s what you need to know about the new math and how to improve your mpg, save money and reduce air pollution.

| August/September 2007

Learn about recent gas mileage calculations and how you can improve your mpg, save money and reduce air pollution.

Gas Mileage Calculations: Why MPG Numbers Really Matter

When Berkeley, Calif., resident Bradley Berman drives his 2006 Toyota Prius around town, the fuel economy indicator pushes into the low 40s. That’s a far cry from the number advertised for the gasoline-electric hybrid, so Berman’s disappointment is understandable.

He says, “When you see 60 mpg on the sticker for city driving, and you’re basically doing city driving but getting in the low-40s, you think ‘That’s terrible!’” Berman’s numbers improve on longer trips, but they still come up short compared to the official miles per gallon estimate for the Prius. Berman should know. As the founder and editor of, he hears from numerous hybrid drivers across the country who share similar experiences.

For better or worse, hybrids have become the poster child for vehicles not living up to fuel economy expectations. That may be because hybrid drivers are theoretically more interested in saving oil and thus complain louder; because hybrids display real-time mpg results and thus their drivers are more aware of the results; or perhaps simply because, as the reigning mpg champ, they’re an easy target.

The truth, however, is that advertised fuel economies of all vehicles, including conventional models, have been slowly but steadily drifting from reality for more than two decades.

To remedy these inaccuracies, the U.S. Environmental Protection Agency (EPA) recently changed the way it calculates fuel economy estimates. The new math will first affect the numbers for model year 2008 vehicles. The results will be lower, more realistic city and highway mpg estimates that “help us capture the way Americans are driving now,” says EPA spokesperson John Millett.

8/10/2009 4:42:49 PM

We can all drive more fuel efficient cars starting today without spending a dime – it’s a matter of adjusting our driving habits. I learned a ton at an eco-driving workshop at this summer’s Midwest Renewable Energy Fair. Check out the top ten tips at Happy eco driving Denise Thornton

9/23/2007 8:49:10 PM

"There is no insult like the truth" Hybrids are the latest crop of Americans wanting absolutely everything for absolutely nothing. The Geo Metro got better real world millage than than any of the current crop of hybrids. It did so with 1/2 the moving parts and 1/4 the price. But Americans don't want sensible cars that get fantastic gas millage with reasonable compromise. Americans want rolling lifestyles with all the gewgaws of home. AND fantastic millage. AND a good price. AND AND AND. No amount of technology can give you something for nothing. Responsible living requires sacrifice and discipline.

9/23/2007 7:20:38 PM

tc is absolutely correct. Come on - making flagrant comments like that (without supporting facts) leads to misinformation and people ranting about non issues. Too much of that already happens. BTW: I have been very annoyed with my 1999 VW Passat and the fact that its impossible to get within 20% of its rated mileage, regardless of driving habits. However, the Passat is quite a lemon and not does not necessarily serve as a good indicator.

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