Washington ? Cars and trucks averaging 62 miles per gallon? Seems extraordinary now, but the government suggested Friday that automakers could be required to build new lineups by 2025 that make today’s high-mileage hybrids seem conventional and turn gas guzzlers into relics of the past.

It’s all included in potential efficiency ranges the government is considering for new cars and trucks starting in 2017. By a decade and a half from now, in 2025, a carmaker’s fleet of new vehicles may need to meet a standard somewhere from 47 mpg to 62 mpg, the Transportation Department and Environmental Protection Agency said.

Those mileage gains that would be the equivalent of an annual decrease in carbon dioxide emissions per mile of 3 to 6 percent.

The new standards, while several years away, are closely watched by the auto industry as it develops future vehicles and environmental groups trying to curb oil dependence and reduce greenhouse gas emissions. President Barack Obama has pushed for tougher fuel efficiency standards, and new rules could take on added significance if Congress is unable to pass energy legislation capping greenhouse gases blamed for global warming.

The government envisions gas-electric hybrids making up about half the lineup of new vehicles under the most aggressive standards, while electrics and plug-ins would comprise about 10 percent of the fleet.

After little progress during the past three decades, rules adopted earlier this year will lift the new vehicle fleet average to 35.5 mpg by 2016, an increase of more than 40 percent over current standards.

The administration’s release on Friday of a technical analysis started the work on mileage standards for the 2017-2025 model years. The government intends to issue a proposal in September 2011 and a final rule by late July 2012.