hypermiler n. A person who attempts to maximize gas mileage by using driving techniques that conserve fuel.
—hypermiling pp.
—hypermile adj.

“When I see someone roar past me, I think, `They just used enough gas to last me a week,’” she said.

She is part of a small and extremely dedicated group of drivers around the country who call themselves “hypermilers.” They almost exclusively drive hybrid vehicles, and their goal is simple: squeeze every mile they can out of each drop of gas.
—Chris Williams, “’Hypermiler’ drivers try to squeeze every mile they can out of a gallon of gas,” The Associated Press, May 29, 2007