While the rest of us are getting fat on fried food and kissing our Ben Franklins goodbye at the gas pump, Ali Sherbiny and Erin McKelvy are eating dark green leafies and getting around -- when necessary -- in a Mercedes-Benz that has consumed only one big Ben this year.

When it comes to diet, the recent Virginia Tech grads and Blacksburg residents are vegans.

When it comes to fuel consumption, they're greasels.

"We're using grease," Sherbiny explained, "and we haven't been traveling much."

In March, 2004, Sherbiny and McKelvy decided to bypass Cancun and use their spring break for a trip to Drury, Mo., in the 1983 Mercedes 300 station wagon the couple bought used for $5,000.

"You can drive out there on diesel and come back on grease," the 23-year-old Sherbiny said, explaining that a Drury company called Greasel Conversions installed the equipment that changed the way they travel.

"Any diesel engine is capable of running on grease."

Vegetable oil -- or grease, as Sherbiny calls it -- was in the picture even when the forward-thinking Rudolf Diesel produced the first diesel engine in 1893.

In 1912, the inventor proclaimed that "the use of vegetable oils for engine fuels may seem insignificant today. But such oils may become in the course of time as important as petroleum and the coal tar products of the present time."

For Sherbiny -- and other environmentalists -- the time has come.

"We take our resources for granted," he said. "I might be driving down Interstate 81 and right behind me and beside me and all around me are these SUVs that get terrible gas mileage and tractor trailers that get no more than five miles per gallon.

"They're doing the bulk of traveling in this country."

In the past year, Sherbiny said he and McKelvy -- who is currently visiting Ireland -- have spent only $100 on diesel fuel for the car they use mainly to haul Sherbiny's musical equipment to and from in-state gigs.

Occasionally, they attend conferences on social justice in Washington, D.C., and Asheville, N.C. They rely primarily on grease salvaged from restaurants to get them where they need to go.

Waste cooking oil is free and most restaurants are happy to donate it to avoid paying a fee to have it hauled. But Greasel Conversions cautions its customers to avoid "fast food places and chain restaurants" because "they tend to have nasty oil and are less likely to let you have it."

Japanese and Chinese restaurants, Greasel's Web site notes, seem to be best, prompting scoffers to quip: "If you fill up on Chinese grease, does your car get hungry 30 minutes later?"

"Ha-ha!" responds Abraham Mwaura, 25, a community organizer for the Ohio Valley Environmental Coalition in Huntington, W.Va.

"I get about 50 miles to the gallon on veggie oil," he said, noting that his 1999 Volkswagen Jetta -- like McKelvy and Sherbina's Benz -- is equipped with a conversion kit that modified the fuel delivery system so the vehicles can run on straight vegetable oil when diesel fuel is used to heat the oil at the start of a trip and to flush the injection system at the end. Both kits came from Greasel Conversions.

"The original kit cost $1,000 and I'm really disappointed in myself," Mwaura said. "It's all stuff available from a NAPA store. I did the conversion with my dad and my younger brother. There's actually not much to it."

Sherbiny and McKelvy also paid $1,000 for their kit.

Greasel Conversions installed it and gave them a step-by-step tutorial on how grease power works.

"You've got to introduce a heating element of some sort into the grease tank," Sherbiny explained.

"It's like if you put olive oil in the refrigerator, it gets chunky. To operate the engine, it has to be fluid. The way you heat your oil is to split the coolant line and send it to a heat exchanger. You need a small amount of diesel to heat. You have to use the diesel the last five minutes of running to purge the system of grease."

Sherbiny said the most important thing to remember is that used vegetable oil must be well-filtered -- a job, he said, that's not so bad if you don't mind dirty hands.

The veggie oil, Mwaura added, has to be heated to a minimum of 170 degrees to be the same viscosity of diesel fuel.

"I travel a lot," he said. "Last year alone, I put 35,000 miles on my car because of work."

"It works well," he insisted.

Both Sherbiny and Mwaura agree, however, that oil-fueled cars aren't the end-all answer to the nation's dependence on fossil fuels.

"I don't think it's the solution. If everyone were to run their car on grease, we would need lots of grease," Sherbiny noted.

"Is it the wave of the future? No, there's not enough vegetable oil out there," Mwaura said.

"My expectation is that we will start seeing more vegetable-based fuels used. My guess is it won't be straight vegetable oil. It will be biodiesel."

Biodiesel, the other alternative fuel to diesel, is a blend of diesel and vegetable oil. It does not require modification on the car's engine, but it is currently more expensive than straight diesel fuel.

Traveling in a car that runs on straight vegetable oil, Mwaura added, provides a constantly changing olfactory experience.

"Sometimes, it smells like a french fry. Sometimes it smells like a fish fry. Once, it smelled like a roasted peanut."

Nationally, only about 5,000 car owners have converted their diesel cars or trucks to run on used vegetable oil.

But Mwaura, who says he probably has the only grease-powered jalopy in Huntington, expects that will change.

Several people -- including one Catholic priest -- have approached him for information that might provide an answer to their prayers.

"The reality is that we should have been looking at alternatives years ago," he said.

"This is going to be less and less radical as gas prices keep going up. I think I'm proving it this week."

For more information on Greasel Conversions, visit www.greasel.com.