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 m.p.g. to 62 m.p.g., the Transportation Department and Environmental Protection Agency said.
Those mileage gains would be the equivalent of an annual decrease in carbon dioxide emissions per mile of 3% to 6%. Industry is watching closely
The new standards, while several years away, are closely watched by the auto industry as it develops future vehicles and environmental groups try 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 make up about 10% of the fleet.
After little progress during the past three decades, rules adopted this year will lift the new vehicle fleet average to 35.5 m.p.g. by 2016, an increase of more than 40% over current standards.
The administration's release on Friday of a technical analysis started the work on mileage standards for the 2017-25 model years.
The government intends to issue a proposal in September 2011 and a final rule by late July 2012.
Friday's "notice of intent" provides an overview of the possible standards, describes the technologies that would be needed to achieve the goals and seeks feedback from the public.
The two federal agencies plan to issue a second notice by Nov. 30 with an updated analysis of potential efficiency targets.
Environmentalists have sought requirements of at least 60 m.p.g. by
2025, arguing that more gas-electric hybrids, electric vehicles and cars and trucks with improved internal combustion engines and reduced weight could dramatically alter the cars and trucks Americans drive."The auto industry has 15 years to meet these new standards -- that's plenty of time to use innovation and technology to reach 60 m.p.g.," said Brendan Bell of the Union of Concerned Scientists' clean-vehicles program.
Automakers, who plan their vehicle offerings years in advance, cautioned that pushing gas mileage standards up too quickly could force them to raise prices beyond the reach of many consumers.
Dave McCurdy, head of the Alliance of Automobile Manufacturers, which represents General Motors, Ford, Toyota and others, said many of the assumptions "are based on very preliminary and incomplete data at this point and inevitably will change as more information is brought to the process."
The Association of International Automobile Manufacturers, whose members include Nissan, Honda and others, said the regulations need to balance issues such as environmental objectives, costs and meeting the needs of customers.
The documents estimate that the toughest efficiency standards under consideration would add up to $3,500 to the price of each vehicle. But under that scenario, owners would recoup their investment in three to four years and save up to $7,400 over the vehicle's lifetime.