Fuel efficiency of 100 mpg? One team left in $5 million ultra-fuel-efficiency contest.

Fuel efficiency of up to 100 miles per gallon is the goal of Progressive Insurance's 'X Prize' competition and a group from Virginia has made a good showing.

The team led by Charlottesville real estate developer Oliver Kuttner is the only one left in the running for the multimillion-dollar X Prize competition to build a four-seat car that can achieve 100 miles per gallon.

Two of the "Very Light Cars" designed and built by Kuttner's team, Edison2, were the only four-door cars to survive the Progressive Insurance Automotive X Prize's two-week knockout stage at the Michigan International Speedway in Brooklyn, Mich.

"It was as good as you can get," Kuttner said. "We did what we set out to do."

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One of Kuttner's cars reached the equivalent of 101.4 miles per gallon. The other achieved the equivalent of 80.3 miles per gallon.

The X Prize's mainstream competition, which started with more than 80 vehicles designed by teams from around the world, will wrap up with a 10-day on-track test at the end of July.

To win, the vehicle must meet or exceed the equivalent of 100 miles per gallon of fuel, run for a minimum range of 200 miles, and meet a variety of tests for safety, maneuverability, acceleration, braking and more.

If any team manages to win the mainstream competition's $5 million purse, it will be one of Kuttner's two vehicles, as none of the other teams managed to qualify.

"From the mainstream competition perspective, Oliver is the show," said Julie Zona, the Automotive X Prize's director of team development and relations. "It's his competition to lose or win at this point."

Most of the knockout stage's vehicles were eliminated because they failed to reach the round's minimum fuel efficiency standard of the equivalent of 67 miles per gallon.

"This stage proved to be highly challenging for many of our contenders," said Eric Cahill, senior director of the Automotive X Prize, in a statement. "We continue to marvel at the innovations we're seeing, but this is an X Prize and accordingly, a very difficult technical challenge. We applaud the teams that advanced this far in the competition. For those whose journey ends here, we also applaud their efforts and wish them the best of luck in maturing their designs so that consumers can someday benefit from their unique and very promising technologies."

Edison2's vehicles manage to achieve their unprecedented levels of fuel efficiency by virtue of their extremely light weight and low aerodynamic drag. They weigh less than 800 pounds, with nearly every component designed for functionality, simplicity and low weight.

The Very Light Car's lugnuts, for example, weigh a mere tenth of an ounce as opposed to a traditional lugnut's 1 ounce.

Edison2's vehicles run on E85 - a mixture of 85 percent ethanol and 15 percent gas - and are powered by highly efficient 250 cc engines with a maximum of 40 horsepower.

A third vehicle designed by Edison2 is also in the running. The team's alternative two-seat tandem vehicle achieved the equivalent of 97 miles per gallon in the knockout stage, giving it a chance to compete in the finals against four other vehicles for a $2.5 million prize.

Edison2's alternative side-by-side two-seat model was eliminated from the competition during the knockout stage. Eight vehicles advanced in the side-by-side category, which also carries a $2.5 million prize.

The alternative class vehicles must carry at least two passengers and must have a 100-mile range.

As the only team to emerge from the mainstream competition's knockout phase, Kuttner said he felt vindicated for believing plug-in electric cars and hybrids are not capable of achieving the extreme high levels of fuel efficiency. Low weight and aerodynamics, he said, are the key to making it possible.

"We really showed the world that efficiency of the actual car is the way to go," he said. "You can't substitute it."

Kuttner's ambition, he has said, is not merely to produce a viable car that can achieve never-before-seen levels of fuel efficiency. He wants to revolutionize transportation and dramatically reduce consumption of gasoline, thereby ensuring a more sustainable future.

"We're trying to do what the world needs to do in the next decade," he said.

The ultimate goal of the X Prize competition, Zona said, is to put cutting-edge fuel efficiency technology into the hands of drivers.

"It's a springboard," she said.

The X Prize's finals will be held July 19 to 30 at the Michigan International Speedway.

Kuttner said he is confident his team's vehicles can meet the goals of the competition and win.

"We have satisfied every criteria," Kuttner said. He added, however, that "it's never over until it's over."

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