Doug Pelmear said he isn't toying with the engine of 1987 Ford Mustang for the money.
The engineer's tinkering, however, could earn him $10 million and save him plenty more in gas money.
Pelmear, who lives in Napoleon, Ohio, has tweaked his Mustang to get 110 mpg, making the engine nearly five times as efficient as a traditional gas engine, he told the Toledo Blade newspaper.
"We redesigned a lot of different things on the [engine] block," Pelmear told the paper. "It's still a rod-and-piston engine; it just has a lot more electronics on it."
Traditional gas engines operate at 8 to 10 percent, efficiency, while the engine on the Mustang, he said, is at 38 percent efficiency.
He said he could greatly increase even that number if his car used traditional gasoline instead of a mix of gas and 85 percent ethanol.
Pelmear entered his car to win the the $10 million Progressive Automotive X Prize: a race to find an affordable, marketable automobile that gets at least 100 miles per gallon.
"I'm an optimist, and I think people need to know there is hope out there," Pelmear told the Toledo Blade. "That's why I decided to enter the X Prize race. I could have sold this [technology] off, but then people might not have seen it.
Pelmear told television station WNWO that the car hasn't traded power for miles per gallon. Pelmear said the car has 400 horsepower, goes well over 100 mph and can go from zero to 60 mph in three seconds.
"This will bring back the automotive industry when they can sell trucks and SUVs and the models that are almost dead at this time," he told WNWO.