Not only do Autumn Chute and Moxie Stratton get their gas for free, but their car exhaust smells like comfort food -- French fries or egg rolls, sometimes fish and chips. It depends what food was fried in the vegetable oil before they pump the fluid into their fuel tanks.

It's been two months since the 29-year-old college students from Napa converted their '80s-era Mercedes Benzes to run on vegetable oil instead of diesel.

A few years ago, Chute and Stratton's switch to veggie oil may have been laughed off as a pipe dream. But increasingly, driving on vegetable oil is going from fringe experiment to the mainstream.

Brian Friedman, who created LoveCraft BioFuels, said when he embarked on his quest to convert cars to veggie oil three-and-a-half years ago, most people thought he was joking. There was an enclave of interest in Seattle and that was it, he said. Now Friedman can't keep up with the California demand, as he tries to convert cars in his own Los Angeles surroundings, as well as some in Northern California.

"There's something massive coming, you can tell," Friedman said. "The people who are getting interested are not experimental people. They're daily driver, nine-to-five working, middle class people. Now its not, 'Huh, I'm thinking about this,' it's 'How do I get a car?'"

Mercedes Benz diesel cars -- popular among veggie oil converters -- aren't that easy to come by anymore, according to Friedman. After no luck finding one in the alternative-oil-loving Bay Area, Chute enlisted her mechanic father's help tracking one down in the Central Valley.

Now Chute is the proud owner of a 1983 300D Turbo Diesel Mercedes Benz and Stratton found herself a 1982 240D Diesel Mercedes Benz. Both formerly diesel vehicles are now emblazoned with vegetable oil bumper stickers. Stratton said she plans to eventually paint her pale yellow car to resemble a corn on the cob.

In the meantime, the $700 cost of the vegetable oil conversion, performed by LoveCraft BioFuels, has already paid for itself in terms of gas savings. Chute's biweekly commute to San Jose would have cost her at least $115 a month if she were driving on diesel.

Instead, Chute and Stratton get their fuel for free from local restaurants willing to donate used vegetable oil they'd otherwise toss out. The biggest hardship of the veggie switch so far has been the competition the women occasionally encounter from companies who specialize in waste-oil removal. Many of these companies pay the businesses for the refuse oil, which can be recycled into myriad things, including candles and soap.

But overall Stratton and Chute say the veggie-oil crossover hasn't demanded much sacrifice from them. Stratton added that she became fully sold on the veggie oil switch when she realized the retooled engine can still run on petroleum or biodiesel. And vegetable oil can mixed in any ratio with either biodiesel or petroleum.

"It was huge to me that you can mix all three kinds of oil," said Stratton, a first-year medical student at Vallejo's Toro University. "The flexibility blew me away."

Crispy commute

Veggie oil hasn't slowed down Stratton or Chute much.

Both still drive 70-75 miles per hour on the freeway. And both self-described environmentalists derive satisfaction from the fact that their engines generate 90 percent less air pollution than a standard diesel engine.

"It's a return to the original," Chute said of switching to veggie oil, since the first diesel engine, invented by Dr. Rudolf Diesel in 1895, ran on peanut oil.

Chute, who absorbed some of her father's knack for auto repairs, said the conversion was surprisingly simple. It involved taping together the hose carrying hot water away from the radiator to the fuel injection hose. This heats and thins out the vegetable oil, which is naturally thicker than the petroleum today's diesel engines are designed for. Going to veggie oil also requires the installation of a filter, very similar to a boat filter, that removes water and other particles.

Chute and Stratton said a filter is especially crucial if someone is contemplating fueling up on waste veggie oil.

"You don't want to end up with a chicken strip or a French fry in your engine," Stratton said.

Simple solutions

The pair are part of a growing trend of drivers relying on renewable fuels, whether vegetable oil or biodiesel, a more refined fuel derived from vegetable oil and other fats. Though there's no official count of how many Americans are driving on biodiesel or vegetable oil, dozens of Web sites have sprung up in recent years explaining how motorists can cross over to cleaner burning oils and why they ought to.

Chute also believes the couple's transfer to veggie oil is part of a bigger social movement she has dubbed "the low-tech revolution." Chute explained that people burning sustainable fuels are hardly the only ones reverting to older technologies that produce less waste.

For example, hand-pulling weeds, instead of spraying pesticides, is a common choice among organic farmers and gardeners.

Stratton said ditching petroleum dependency was a huge relief for her after years of feeling guilty about the toll of oil-drilling, oil-manufacturing and oil-burning on the land, air and human health.

Detoxifying

Recently, Stratton learned that about half of the car fumes that infiltrate an individual car cabin come from that same vehicle. For Stratton and Chute, that's another sign that their move is healthy. They're reducing their exposure to carbon monoxide and other carcinogenic exhaust by about 50 percent.

The duo also believe relying on a renewable fuel helps reduce the United States' dependency on oil-rich nations for their natural resources.

"If you're running on petroleum all the time you're really under someone else's control," Chute said.

While Chute and Stratton believe choosing a sustainable fuel source makes political sense, they understand others don't share this view.

Chute said she's had encounters with drivers of monster trucks, whose windows were stamped with American flag or National Rifle Association stickers. They honked and yelled obscenities. And it's happened twice to Chute while passing through Martinez, the northeast Bay Area city that's home to a sprawling oil refinery.

"A lot of people seem to think you can't be environmental and concerned about people's jobs and the economy. But I imagine they could work at a biodiesel plant," Stratton said.

"People would just be handling different substances," Chute said, noting that the byproducts of corn and soybeans are significantly less toxic than those of petroleum.

Both Stratton and Chute are finely attuned to which industries emit toxic byproducts. Both were exposed as children to high levels of toxic contamination they believe led to health troubles in their adult lives.

Chute recalled growing up in the small Central Valley town of Dinuba. She can't count the times she and her brother played outside as pesticides were sprayed on orange groves all around them.

Meanwhile, Stratton grew up in south San Jose, near the former Fairchild Semiconductor facility which -- according to the Environmental Protection Agency -- polluted a public well when an underground waste tank failed in 1981.

As young adults, both Chute and Stratton suffered from auto-immune disorders that have been linked to overexposure to toxins.

Now Chute and Stratton are committed to making non-toxic consumer choices as often as possible. They say converting to vegetable oil powered cars is just one part in that lifelong mission.

"I understand and I think most people understand, without knowing all the details and chemistry, that cars are bad for the environment," Stratton said.