For years auto scribes have questioned why Japanese V-6s, such as the 270 horsepower motor in the 2005 Acura TL sedan, seemed more powerful than many American V-8s. Now we have some answers. For 2006, Acura claims only 258 hp for the TL's 3.2-liter V-6.
It is not $3-per-gallon gasoline or a retreat from the industry's ongoing horsepower race behind the revised statistics. Acura and other automakers had to restate power ratings in order to conform to a new standard promoted by the Society of Automotive Engineers, a professional technical organization.
"The committee took a look at the existing horsepower standard and found areas open to interpretation," says SAE spokesperson Gary Pollak. Under the previous documentation, companies had more latitude in the testing process to select fuel grades, fiddle with electronic control units or exclude accessories like power steering. "The new standard has no ambiguities," says Pollak.
Nameplates such as Acura and the Lexus division of Toyota Motor (nyse: TM - news - people ) have quietly restated figures on a number of models. For 2006, the high-end Lexus LS V-8 sedan, the 430, for example, drops to 283 horsepower from 290, while the V-6 in the Lexus RX 330 fell to 223 hp from 230. In contrast, numbers went up a bit for some motors from Pontiac and Buick.
SAE added another twist: voluntary outside verification of horsepower tests. So far, only General Motors (nyse: GM - news - people ) and DaimlerChrysler (nyse: DCX - news - people ) have taken this extra step--at least on a few engines. Some GM engines went down in advertised power. But under the new standard the horsepower promised in the new super Corvette motor, the LS7, went up to 505 from 500.