Will the EPA Change the Way It Measures M.P.G. Ratings? Maybe Just for Hybrids?

It's widely believed that the mileage ratings of many hybrid cars are inflated. Is it time for the ratings system to change?

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Ford Motor Company

Ford C-Max

Drivers have good reason to be skeptical about m.p.g. claims posted on new-car windows. After complaints and new rounds of testing, the EPA recently had to lower m.p.g. ratings for several Kia and Hyundai models. It’s widely believed that the mileage ratings on many hybrid cars are inflated as well.

Ford, which has come under fire after Consumer Reports’ tests showed that the fuel efficiency of two of its hybrids was off by 20%, is now saying it may be time for the Environmental Protection Agency to change procedures for coming up with the numbers — at least for hybrid vehicles. “We continue to work closely with the EPA to determine whether the industry testing procedure needs changes for hybrid vehicle testing,” Raj Nair, Ford’s product-development chief, said, according to Bloomberg News.

The Kia-Hyundai miniscandal freshly brought to light the fact that for the most part, the EPA doesn’t measure how many miles per gallon each car model gets. Instead, the automakers themselves conduct tests, and the EPA winds up doing audits on about 15% of vehicle models in the hopes of keeping everyone honest. The federal agency also does its own tests after receiving an abundance of complaints from consumers or reports from independent testing organizations like Consumer Reports. This is how Kia and Hyundai models wound up being tested and how the m.p.g. ratings for several models wound up declining.

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Now the EPA is taking a closer look at two Ford hybrids, the C-Max and the Fusion. Both were certified for 47 m.p.g., and both fell well short of that in CR’s tests (37 m.p.g. and 39 m.p.g., respectively). “These two vehicles have the largest discrepancy between our overall-mpg results and the estimates published by the EPA that we’ve seen among any current models,” CR reported at the time it released its test results.

The large discrepancies have left consumers not only confused but reluctant to trust the numbers listed on car-window stickers, prompting some to think it’s time for the EPA ratings and testing systems to change. The problem is especially pronounced with hybrids, the Detroit News reported:

Most vehicles’ real-world gas mileage is less than the EPA sticker number, and can often be 20 percent less than the sticker number depending on speed, temperature and other factors.

With hybrids, however, the gap is much wider — as high as a 30 percent drop, the EPA says. And as the fuel efficiency of hybrids continues to climb, the gap is growing wider between EPA figures and real-world fuel efficiency.

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In particular, the fuel efficiency of hybrids is affected by temperature; Consumer Reports’ tests were conducted in Connecticut on fairly cold days, which explains in part why the cars’ m.p.g. averages were so poor. Even so, Edmunds explained why EPA procedures aren’t likely to change anytime soon:

It doesn’t have the budget, equipment or manpower to test the hundreds of individual models with unique engine and transmission combinations that automakers produce each year.

In other words, the “official” EPA rating is a rough estimate that may be far off the mark because of a wide range of factors, but it’s the best we’re going to get. Therefore, drivers really should take that “your mileage will vary” disclaimer on new-car stickers to heart.

It’s probably smart for consumers to consult other drivers for a better idea of real-world mileage. The EPA website has a shared m.p.g. estimates tool where everyday drivers are invited to track their fuel efficiency — and where the Ford C-Max Hybrid is shown to average 39 m.p.g., with various users reporting their vehicles getting anywhere from 31 to 56 m.p.g.

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“Honestly assessing your specific situation is the only way to adjust the EPA ratings down — or up — to more accurately reflect the fuel economy you can expect to see once the car or truck is yours,” is the suggestion from Edmunds. “One way to do a reality check on a car’s EPA rating is to deduct 10 percent from it if you consider yourself an aggressive driver. This means someone who routinely exceeds speed limits and hurries away from stop signs and red lights.”

Since cold weather can seriously affect the mileage of hybrids, it could also make a big difference if you’re living in Minnesota or Florida.