Automakers would have to achieve sharply higher fuel economy -- between 47 and 62 miles per gallon -- by 2025 under a preliminary plan released by the Obama administration on Friday.
The Transportation Department and the Environmental Protection Agency issued a preliminary fuel efficiency proposal to industry that is not expected to be finalized until 2012.
Industry comment is being sought on the plan which proposes annual efficiency gains of 3 percent to 6 percent, or 47 mpg to 62 mpg, from 2017 to 2025.
A 62 mpg standard would save 45 billion gallons of oil and reduce carbon pollution by 450 million metric tons by 2030, according to the Natural Resources Defense Council, which was briefed by administration officials about the plan.
Passenger vehicles emit about 20 percent of the nation's carbon emissions and consume about 44 percent of its oil, figures show.
Standards imposed last year require automakers to achieve 35.5 mpg by 2016, up 42 percent from current levels.
(Reporting by John Crawley, Tom Doggett and Timothy Gardner; editing by Jim Marshall)