(MONEY Magazine) – Jonathan Pratt, like any small businessman, delights in small victories. Take, for example, the $1,500 worth of huitlacoche (a.k.a. Mexican truffles or corn smut) he scored from local farmers for free. "They were going to throw it out," says Pratt, who's now piling the stuff into chiles rellenos at his two Ümami Cafés in Westchester County, N.Y.

But he's even happier with his latest truck. Until recently, he paid $200 a month to dispose of the oil his restaurant uses to fry potatoes. At the same time, the gas bills for his truck hit $700. Then his partner recalled that farmers used to run tractors on vegetable oil. Inspired, Pratt bought a diesel-powered Ford F250 on eBay for $11,000 and paid $1,500 to have it hauled from Arizona ("Nothing rusts in Arizona," he says). Next came an $850 conversion kit through greasecar.com. (The folks at Greasecar, which sells $800-and-up kits to convert most diesel engines to run on vegetable oil, say business is up 500%.) With the $900 in monthly savings on fuel and grease disposal, Pratt figures he'll recoup his costs in 14 months. Plus, he has the best-smelling truck in town. "If you get your oil from a Chinese restaurant, it smells like egg rolls," he says. "Mine, of course, smells like french fries." Which explains the sign he's ordered for the rear bumper: IF YOU LIKE WHAT YOU SMELL, FOLLOW ME TO ÜMAMI CAFÉ. —JEAN CHATZKY