CAMDEN, Maine — Whenever the Dirigo rolls into town, heads turn. And that’s before onlookers learn that the three-wheeled car is capable of getting 90 miles per gallon.

With its rounded shape, shiny wood finish and retro charm, it doesn’t look like a car that is years ahead of its time, but Camden boat builder Bill Buchholz hopes that the interest generated by its unusual appearance will help get the message out about the future of transportation.

“People respond to this in such a unique and positive way,” he said of the Dirigo, the state’s Latin motto that means “I lead.”

“This car should be leading the discussion in some way on efficiencies,” he said.

The inspiration for the Maine-made, ecofriendly auto came in 2007, when a group of cool-car enthusiasts, engineers and builders gathered in the midcoast to brainstorm ideas for the international Progressive Insurance Automotive X Prize. The $10 million purse for the contest, held in 2010 in Michigan, was designed to inspire the design and construction of practical cars that could achieve 100 miles per gallon. Other goals included benefiting the world and educating the public.

The eventual winner of the Mainstream Class, Oliver Kuttner of Charlottesville, N.J., took home a $5 million prize for his team. Their car achieved 102 miles per gallon.

At first, the Maine competitors kept busy dreaming up ideas in the conference room of the Camden Public Library. Then they moved the operation to a Lincolnville garage to make the Dirigo a reality. Some key features included side-by-side seating, a diesel-powered engine in the back and a “tadpole trike” design. Two wheels in front and one wheel in back is both stable and aerodynamic, Buchholz said.

The group received some financial support and applied for nonprofit status in order to create the “Maine Automotive X Team.” They bought a Kawasaki Mule all-wheel-drive vehicle, disassembled it, then reassembled some pieces along with other components into what eventually would become the Dirigo.

By this time there were just four key team members left: Evan Schmidt of Islesboro, Rick Pierson of Northport, Bob Bailey of Appleton and Buchholz. Team members gathered every Saturday morning to work on the vehicle. They finished in the spring of 2009.

“I think because it didn’t belong to anybody, we were free to think of the car and not politics,” he said. “It was a nice creation exercise.”

What they created cost an estimated $15,000, not including their time, and is inspected in Maine as a modified motorcycle. The diesel-powered Dirigo’s body weighs just 120 pounds, with a metal roll cage encased in quarter-inch planks of western red cedar from Viking Lumber.

In the end, the small team ran out of time and money for the entrance fees and all the paperwork necessary to compete for the prize.

“There was a lot more to do than just build the car,” Buchholz said. “We didn’t have the horsepower.”

Even without a shot at the X Prize, team Dirigo believed they had achieved something pretty special with the car.

Just how special became more clear when Buchholz and Schmidt entered the Dirigo in the Green Grand Prix in Watkins Glen, N.Y., for its maiden competition.

The Dirigo had not been superefficient right off the blocks, Buchholz said. On its first trip, he made just 49 miles per gallon on underinflated tires, which was a big disappointment.

So, hoping for the best but fearing the worst, Buchholz and Schmidt used a Saab to tow the Dirigo toward the Green Grand Prix, a competitive educational road rally held in New York State. With 200 miles to go, the Saab broke down. The men put their tools in the Dirigo and hit the road on a rainy night in the relatively untested car. Driving as fast as he could over mountain roads in the heavily loaded car, Buchholz eked out 55 miles per gallon. Better. But not perfect.

“It was not what we wanted,” he recalled.

Then, during the 90-mile road rally loop around Lake Seneca, as Buchholz drove very carefully to maximize the mileage, the Dirigo began to drive up to its potential. It made it to 89 miles per gallon, good enough to receive second place overall in a field of 30 cars. The winner was a highly modified Geo Metro that got 99 miles per gallon, Buchholz said.

“I felt great,” he said. “We were ecstatic. We had just built this thing. We didn’t know what to expect. We were grinning the whole way back to Albany.”

He’s also smiling about the 2010 Rally Green, an event the Dirigo team organized that was designed to show people across the country that superefficient cars are a thing of the present.

“We thought we should do something really big,” Buchholz said.

The rally, a five-day trek from Iowa to California, had just three cars at the starting line. On the first day, one car broke down and was out. The other car broke down “every day,” Buchholz said.

“The Dirigo is the only car that did it,” he said.

Crossing the Continental Divide was hard, with the Dirigo “weak and hot” at 12,000 feet. But it made it.

“Everywhere I went, people came out to look and ask questions,” he said. “They were all positive. It gave me hope that people are thinking about this as a major issue.”

The Dirigo isn’t the solution to the world’s fuel problems. He knows that. The diesel engine is noisy and some drivers would consider it unsafe.

“In a direct side-impact crash it would not be a very pretty picture. But that’s life. There are no guarantees,” Buchholz said. “I’m finding out that if we make safety a major consideration, we’d all end up driving tanks. I don’t think we can afford to be driving tanks.”

However, Europe has many small, highly efficient cars and Buchholz thinks it’s time for more to come to the United States. Throughout the Dirigo process, he said that he learned that low-mileage vehicles are a matter of political will and not technology.

“I’m more interested in the politics of this transportation problem we have,” he said. “I understand we need to use less gasoline because fuel is limited. Ninety percent of the energy is used to move the car and not you, because cars are just so big and heavy. And if we can just conserve oil for a longer amount of time, it will allow us to research the next thing.”

While Buchholz said he’d be thrilled if a major automotive company became interested in the Dirigo, he doesn’t expect that. A more likely outcome would be that people who notice him tooling around midcoast Maine in the Dirigo may be inspired to ask questions, first of him and then of others. He would love it if Americans would drive in droves to car dealerships to demand cars with good gas mileage.

“If we all did that, it would get Detroit’s attention,” he said. “If four guys in Maine can build a decent car and drive it halfway across the country, and get 90 miles per gallon — they have the technology, too.”