Gawkers couldn’t have known that Mr. McCornack and Ms. Westcott had just driven the vehicle more than 800 miles over three days from Berkeley, Calif., but many nonetheless noticed the plastic tank of vegetable oil — a.k.a. fuel — affixed to the back.

In making it to Las Vegas in a total of 1,418 minutes without burning an ounce of petroleum, the duo from Cave Junction, Ore., collected a $5,000 prize in the Escape From Berkeley race.

“We signed up to do this before we even knew there was money involved,” said Mr. McCornack, owner of Kinetic Vehicles, a maker of alternative cars, his face ruddy and his hands chapped from the constant sun exposure. “It just seemed like great fun.”

Fun, perhaps, but also quite a challenge. The five teams that began the race on Saturday dwindled to just two by Monday’s start because of mechanical problems on the other makeshift vehicles that paid $500 to enter.

Beyond the requirement to use no petroleum products for fuel was the added twist that the participants would have to scavenge along the way for raw materials. They weren’t allowed to buy any, but Mr. McCornack and Ms. Westcott were delighted by donations of oil from local people who would ask questions about the odd-looking vehicle as they stopped outside of grocery stores. For the favor, the duo gave out bright yellow T-shirts commemorating the race.

“I’m actually kind of shocked that anybody made it at all,” said Jim Mason, the event’s organizer and founder of a 20,000-square-foot open-air garage in Berkeley called Shipyard Labs where self-described “geeks and gearheads” work in shipping containers. “It’s a pretty high bar to set to say you can use absolutely no petroleum and you can start with one gallon of whatever your fuel is and you gotta drive 600 miles. It was pretty possible nobody would even make it here and I was fine with that.”

Indeed, the original route led drivers through the 9,943-foot-high Tioga Pass in the Sierra Nevada mountain range, but that pass was closed due to a snowstorm. That meant a 200-mile detour.

Mr. McCornack’s sole rival by Monday was a green Dodge=2 0Dakota that runs on oxygen, hydrogen and methane power converted from burned wood in a large black contraption. The vehicle was driven by Wayne Keith, a 59-year-old cattle rancher from Springville, Ala. Mr. Keith stopped using petroleum for his vehicle five years ago when gas soared to $1.75 a gallon.

Though Mr. Keith arrived at the Sahara first on Monday, he finished about three hours behind Mr. McCornack and Ms. Westcott in total travel time over the three-day trip due to trouble Sunday with a flat tire and a some dead wood that didn’t burn properly. He used a variety of biomass along the route for the truck, which he says runs on the equivalent of a penny a mile in fuel costs.

“You name it, switchback, kudzu, corn starch, cotton starch, newspaper, corn cobs, phone books,” Mr. Keith said. “Its all carbon neutral. This is more clean than an electric car.”

Mr. McCornack also bragged about the low fuel cost, its environmental cleanliness and its efficiency: “Normally, we can get 60 or 70 m.p.h. on this, but we had so many hills and such headwinds, we spent a lot of time in the 40s.” Both teams that completed the race faced unusual olfactory challenges as well. They ate little while traveling so as=2 0to not waste time, but Mr. McCornacks vegetable oil evoked the scent of French fries. Mr. Keith admitted the burning biomass in his flatbed made him crave barbecue.

Among the vehicles that didn’t make it were a Mercedes-Benz that runs on vegetable oil, a two-man bicycle augmented by a one-horsepower electric motor that runs on ethanol, and a 15 m.p.h. steam-powered three-wheeler (two of which are wooden).

Mr. Mason chose Las Vegas to complete the race largely out of contempt for the tourist destination, he said.