Fuzzy math on new car mileage stickers

If you have been looking at cars in dealers showrooms recently, you may have noticed that new car “window sticker” mileage ratings are lower than they were before September 2007.

A little less than two years ago the Environmental Protection Agency (EPA) decided to revise the tests it uses to determine the official fuel-economy rating for new automobiles.

It was no secret that before the revision, the actual gas mileage delivered by a new car tended to be significantly lower than what was promised by the official “window sticker” ratings.

The new EPA tests account for more realistic vehicle operation - faster driving, acceleration and deceleration and air-conditioning use.

As a result fuel-economy ratings have dropped about 12% for city driving and about 8% for highway driving. When the new tests kicked in, a 2006 Toyota Prius, for instance, went from having a 55 m.p.g. combined efficiency rating to 46 m.p.g. — overnight.

Now, when buying a new car, the “window sticker” mileage ratings won’t be as attractive but they will be more accurate.

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