For now, NHTSA says that it's only evaluating the impact of boosting fuel economy by the aforementioned amount and that it has already reached a "tentative conclusion" that seven percent is the maximum feasible increase. In a May 10 Federal Register notice, NHTSA wrote that it will thoroughly evaluate the costs and environmental effects of increasing CAFE standards before publishing its proposed rule this September, according to Automotive News ( sub. req.).
Existing fuel economy standards say that by 2016, automakers must hit a fleet-wide average of 34.1 miles per gallon. Last year, the U.S. Department of Transportation and the EPA proposed a CAFE standard of 62 miles per gallon by 2025.
[Source: Automotive News – sub. req. | Image: Joseph Jayanth - C.C. License 2.0]