Two years ago, Goodwin got a rare chance to show off his tricks to some of the car industry's most prominent engineers. He tells me the story: He was driving a converted H2 to the SEMA show, the nation's biggest annual specialty automotive confab, and stopped en route at a Denver hotel. When he woke up in the morning, there were 20 people standing around his Hummer. Did I run over somebody? he wondered. As it turned out, they were engineers for GM, the Hummer's manufacturer. They noticed that Goodwin's H2 looked modified. "Does it have a diesel engine in it?"

"Yeah," he said.

"No way," they replied.

He opened the hood, "and they're just all in and out and around the valves and checking it out," he says. They asked to hear it run, sending a stab of fear through Goodwin. He'd filled it up with grease from a Chinese restaurant the day before and was worried that the cold morning might have solidified the fuel. But it started up on the first try and ran so quietly that at first they didn't believe it was really on. "When you start a diesel engine up on vegetable oil," Goodwin says, "you turn the key, and you hear nothing. Because of the lubricating power of the oil, it's just so smooth. Whisper quiet. And they're like, 'Is it running? Yeah, you can hear the fan going.'"

One engineer turned and said, "GM said this wouldn't work."