The United States Environmental Protection Agency is preparing this fall to release to the public an audit of carmakers’ fuel economy claims. Christopher Grundler, head of the EPA's Office of Transportation and Air Quality, told Automotive News in an interview last week that the results of industry-wide audits included tests on over 20 car and light-truck models this year.
The audits were done at tracks in Arizona and Michigan and were intended double-check carmakers' readings on the "coast-down" test, which turned up problems with the mpg figures on several Hyundai and Kia's window stickers in 2012. Grundler said he can't comment on the EPA findings until he talks to his bosses and briefs executives from carmakers. He, however, said that the report "will be very interesting to some people."
The coast-down test involves speeding a vehicle to around 80 mph and then allowing it to glide to a stop. This process measures the aerodynamics of a vehicle, the rolling resistance of its tires and the amount of friction in its drivetrain. The measurements are used to program a dynamometer to run the vehicle through the EPA's test cycles and come up with mpg estimates.
There has not been a regular audit of the coast-down figures that carmakers submit until 2010, when Grundler's predecessor, Margo Oge, ordered an initial round of audits aimed at deterring cheating at a time when customers are increasingly factoring in fuel economy in their buying decisions. The EPA has already briefed carmakers on audit of their cars in the summer, but the release this fall would be the first time that the figures would be made public.