Leisure

Converting an old Mercedes to run on cooking oil saved me dollars but nearly ruined my marriage

By: Greg Melville; Photographs: Andrew Hetherington
Published: February 2008   [ Updated: Jul 14, 2008 - 2:43:41 PM ]

She no longer has a great body. Her rear end sags, her skin shows the splotches of age, and she’s a tad too curvy for modern tastes. But through my rose-colored Oakleys, I still see a pale, near-perfect German goddess—all six cylinders and 3,500 pounds of her. She is my cream-colored 1985 Mercedes 300 turbo diesel station wagon, and she runs on cooking oil.

The more time I spend doting on her, the more jealous my wife gets. Ann Marie thinks my weekends would be better spent by, say, paying more attention to our two kids. She simply doesn’t remember what it’s like to fall in helpless out-of-control love.  

It was actually Ann Marie’s idea, converting a car to run on used vegetable oil from restaurant fryers. She and I wanted to do more for the environment than mail the occasional check to the Sierra Club. She convinced me this would cut down our greenhouse gas emissions and flip the bird at Halliburton and Exxon Mobil. We found our Mercedes for sale about an hour south of us in Vermont, with 265,000 miles on the odometer, a few rust spots on the doors, only three working stereo speakers, and a small oil leak. Otherwise, the old girl was in decent shape.

Not long after we got her home, I called Greasecar, a Massachusetts company that makes veggie-oil conversion kits. The setup is fairly simple. Basically, a 15-gallon aluminum tank is installed in the trunk of a sedan or in the rear compartment of a wagon, and hoses connect it to the engine. No major mechanical engine modification is needed with the kit, thanks to Rudolf Diesel himself.

At the World’s Fair in 1900, Herr Diesel introduced his engine to operate on peanut oil. Petroleum-based diesel became the gas of choice because it was—and still is—easier to produce and slightly cheaper. (Jugs of pure vegetable oil go for about $3 a gallon at Costco.) Veggie oil also congeals at a much higher temperature than petro diesel, so starting the car on cold mornings would be nearly impossible.

But my converted Mercedes uses waste vegetable oil, which restaurants are usually happy to give away for free. The Greasecar system also eliminates the vegetable-oil gelling problem; the car engine starts by using regular old petro diesel in the regular old gas tank. As the engine warms, hot coolant is diverted to heat the veggie oil in the tank in back. After the car is fully warmed up, just press a button mounted on the dash and you’ve switched fuel sources on the fly. The fuel I’m talking about shouldn’t be confused with biodiesel, which is vegetable oil that has been refined into a pure, bona fide fuel with the viscosity of petro diesel.

To me, the greatest advantage of driving a grease-powered car isn’t its beneficial impact on the environment—though its emissions are much freer of pollutants and carbon dioxide than one that runs on unleaded—but its beneficial impact to my paltry writer’s bank account. I drive for pennies a mile. Yet approaching a potential supplier feels a lot like meeting a pot dealer in a new town for the first time: There’s the awkward initial proposition; the fear of rejection followed by the actual illicit transaction (according to the EPA, driving a veggie-powered car subjects the owner to a $2,750 fine, but I don’t think anyone has been busted yet).