The Willow Glen resident hasn't constructed a sinister plot to cause people to dump their diets; instead he has adopted a unique way to save money while helping the environment.

In September 2005 Danais had the diesel engine of his recently purchased 1993 Mercedes Benz converted to run on used vegetable oil, a clean-burning renewable alternative to fossil fuels. He currently spends about $8 a month to fuel his car.

Danais' interest in this alternative source of energy started brewing four or five years ago after he read an article about someone who drove a Volkswagen diesel van across the country, stopping at McDonalds to fuel up.

"I thought, 'How can that be?' so started investigating," he says.

Danais found the story was legitimate and consequently purchased a car he could convert.

"The conversion cost about $1,500, but it can be done for much less depending on a person's mechanical aptitude," Danais says.

Though he declines to name them, Danais picks up oil for free from local restaurants.

"They are more than willing to give up their used oil because what I don't use, they have to pay to dispose," he says.

He adds that he also saves the oil from his own cooking forays and those of his friends and neighbors. And, because the oil is noncombustible, it can be safely stored in a tank in his garage.

The conversion of Danais' Mercedes consisted mainly of adding a 15-gallon tank in his trunk to hold the vegetable oil and a system to heat the oil. The car's regular diesel tank supplies fuel to the engine at start-up. Once the engine is running, the warmth produced is used to heat the vegetable oil and reduce its viscosity so it has a consistency similar to diesel fuel and can be injected into the engine. Once the vegetable oil has reached a proper viscosity, Danais flips a switch on the dashboard and the car begins to run solely on the vegetable oil.

"Generally it takes four to five minutes of driving before the oil is liquid enough to run through the injectors, though it all depends on the temperature outside," he says. "An 80-degree day requires less time than a 40-degree day."

This type of conversion technology is available only for diesel-fueled vehicles. It is not designed for vehicles running on unleaded gasoline.

While traveling around town on errands, Danais can stop and restart the car using the vegetable oil. If the vehicle is shut down for a long period of time, however, the vegetable oil will cool. Then it must be purged from the fuel system and replaced with diesel until the next start-up. Danais accomplishes this simply by flipping the dashboard switch back to its original position and driving for a few miles.

Danais says he doesn't notice any difference in engine performance on either fuel source, and the miles per gallon are the same with either fuel.

The use of plant-based oil in diesel engines is not a new concept. When Rudolf Diesel introduced his revolutionary engine at the 1900 Paris Exposition, he related that he designed the engine to run on peanut oil so farmers could grow their own fuel. In fact, most diesel engines were run on vegetable oil until the 1920s, when the petroleum industry promoted a gasoline byproduct as diesel fuel.

According to the Environmental Protection Agency, vegetable oil burns much cleaner in a diesel engine than diesel fuel. The burned oil emits no sulfur and does not contribute to acid rain. In addition, the carbon released when the oil is burned is what would have been released naturally from the decay of the plant matter. Fossil fuels, on the other hand, release carbon captured millions of years ago, which upsets the atmospheric balance. This release of carbon is considered a factor in global warming.

"I am not a do-gooder or a tree-hugger, but the fact is glaciers are melting and crazy storms are plaguing the planet," Danais says. "Lots of people, like me, think this is happening because of the burning fossil fuels."

Although Danais prefers to run his car on used vegetable oil, biodiesel fuel is another option for people who do not want to convert their diesel engines. Biodiesel is also a plant-based fuel, but it has been chemically altered to remove the glycerin, which causes the oil to congeal. As a result it does not need to be heated and can be poured into a regular diesel tank.

Environmental issues aside, the idea of vegetable-based oil running in a car could be considered patriotic.

According to the National Biodiesel Board, a trade association representing the biodiesel industry and a coordinating body for research and development in the United States, American farmers could grow fuel to supply the country's needs, thereby helping the country's economy while simultaneously reducing the nation's dependence on foreign oil.

The idea has also captured the attention of the EPA. The agency is working with the biodiesel industry on a variety of clean- air programs, along with a renewable fuels standard, to help achieve the current federal administration's goal of replacing more than 75 percent of oil imports from the Middle East with alternative sources of energy by 2025.

In a press release issued on Feb. 6, EPA administrator Stephen L. Johnson said, "Twenty-five years from now, we can make foreign sources of oil go the way of the typewriter and the Walkman."

For Willow Glen residents such as Danais, that day is now, as he drives around town with the smell of french fries streaming out of his exhaust.

More information about diesel conversion vehicles can be found at biodiesel.org.