I didn't realize this, but the current fuel economy standard for cars, unchanged since 1983, is 27.5 miles a gallon. Light trucks, including S.U.V.’s, pickups and minivans, must achieve a minimum average of 21.3 miles a gallon over each carmaker’s entire fleet. I guess that explains how they can get away with making Hummers that get 10-12 miles per gallon. Under the proposed legislation, cars would have to achieve an average fuel economy of 36 miles a gallon by 2022, while trucks would have to reach 30 miles a gallon by 2025. It's a start.