The 2008 model of the popular Toyota Prius hybrid, for example, is now estimated to get 46 miles per gallon overall, compared with the 55 miles indicated on window stickers for the 2007 version, a 16.36 percent decrease. But like other cars, the 2008 Prius is not actually using more fuel than its predecessor. The plunge reflects a reality check from the Environmental Protection Agency, which has revised its mileage calculations to better reflect actual driving conditions.
Under the new EPA testing criteria, the average miles per gallon for 2008 cars and light trucks will fall about 12 percent for city driving and 8 percent on the highway. The numbers for some hybrids will tumble even more - by 20 to 30 percent for city driving and 10 to 20 percent under highway conditions.
Toyota Motor Corp. said it was not surprised by the lower numbers.
"This is a much more realistic test, and the results are much more in line with what our customers have been telling us," said Toyota spokesman Wade Hoyt.
Even though the lower numbers come at a time when gasoline prices are topping $3 a gallon, visitors attending the New England International Auto Show at the Boston Convention & Exhibition Center yesterday seemed to take the downward adjustments in stride. John Alexander from Providence said he always viewed mileage stickers "for what they were worth." But "if they're doing it more honestly now," Alexander said of the EPA's testing, "that's definitely going to help."
The change in the way the EPA measures mileage performance marks the agency's first revision of its mileage testing in 22 years. The old tests figured an average driver's top speed at 60 miles per hour and included limited acceleration. They were also conducted without the use of air conditioners and other accessories that reduce fuel efficiency. In addition, the tests failed to calculate the increasing amount of time most drivers spend idling in traffic, sudden acceleration, and the effects of cold weather on a car's performance. Now, the EPA incorporates all of those factors into its testing, including highway speeds as high as 80 miles per hour. And for the first time, the sticker estimates include a figure for overall mileage, not just city and highway.
"The hit is really quite substantial across the board," said Therese Langer, transportation program director for the American Council for an Energy Efficient Economy, an independent Washington-based group that monitors automotive efficiency.
And while SUVs and pickup trucks appear to take the softest blow under the revised EPA standards, with many dropping only 1 or 2 miles per gallon, their low-efficiency starting point still yields a significant percentage cut for most models.
The EPA has also recalculated mileage estimates for all auto models back to 1985, so that they, too, better show the actual mileage the vehicles achieve. The revamped figures are available online at fueleconomy.gov. For example, when the new standards are applied to 2007 models, the BMW 328ci drops from an overall rating of 24 to 22 miles per gallon. The 2007 Ford Focus wagon is now listed as getting 27 miles per gallon instead of 31, and Honda's 2007 subcompact Fit drops from 34 to 30.
Gloria Bergquist, vice president of the Alliance of Automobile Manufacturers, which worked with the EPA on the new testing standards, said revised numbers won't appear on all vehicles until the 2009 model year. That means that although the majority of 2008 vehicles have the new stickers, some that went on sale early this year may still have old stickers with inflated mileage estimates.
It is easy to tell whether a car has a new sticker: While city mileage estimates are on the left and highway figures are on the right for old and new stickers alike, the new stickers also include the overall mileage estimate at the bottom center.
(The Globe has not used EPA estimates in its testing of cars, instead relying on 800-1,000 miles of varied driving to establish real-world mileage.)
Despite the potential for confusion because of the way the new system is being phased in, Rik Paul, automotive editor for Consumer Reports, said that "overall, it's a plus for consumers." Paul said the new EPA estimates are much closer to reality, although city figures - particularly among hybrids - are still higher than what Consumer Reports testing has shown.
But the EPA estimates have never taken into account personal driving styles, which can affect mileage. To save fuel, the agency recommends avoiding aggressive driving - including speeding, rapid acceleration, and hard braking. It also recommends removing extra weight from a vehicle - just 100 pounds can translate into a 2 percent drop in fuel efficiency.
Other tips for improving mileage include keeping a car tuned, checking tire pressure regularly, and following a program of recommended oil changes.
Royal Ford can be reached at firstname.lastname@example.org.
© 2007 The Boston Globe