When the cost of diesel skyrocketed to more than $4 a gallon, Travis Sweat fought back. Using knowledge from the Internet and recycled oil from fast-food restaurants, he made his own fuel for $1 a gallon.

“I’d heard of other people (making their own fuel), and I knew there were several different ways to do it,” said Sweat, who has run his 1997 Ford F-250 on a blend of waste vegetable oil for seven months.

Sweat, a game warden from Griffin, Ga., gets free used liquid fryer oil from a friend who owns a restaurant. He uses vegetable, peanut and soybean oils. Hydrogenated oil can’t be used.

Sweat filters the oil twice and puts it through a water separator. It takes 30 minutes to process a 55-gallon batch of fuel. “Basically, I just pour a few things in a drum, filter it and I’m ready to go,” he said.

Sweat’s recipe is 80 percent oil, 15 percent to 20 percent diesel and 5 percent gasoline.

His fuel isn’t biodiesel, which is “harder to make and requires more chemicals,” he said. WVO fuel blend can only run in certain types of engines and injection systems, Sweat said. It won’t work at all in newer trucks.

When Sweat switches his truck from diesel to his WVO blend, he likes the difference. “The engine gets really quiet and smooth, and it runs a lot better,” he said. “There used to be a rough idle at stop signs, and now there isn’t.”

Sweat’s wife, Stephanie, has faith in her husband’s homemade fuel. She must. She drives the truck to work and to run errands around town.

Sweat admits, though, his greatest concern is engine failure.

“It was a little scary at first,” he said. “If you blow a diesel engine, you’re looking at $5,000 to $10,000 to replace it.”

Sweat should be careful, said Dan Geller, a researcher with the University of Georgia College of Agricultural and Environmental Sciences. From an engineering standpoint, the fuel he’s burning won’t work for long.

“The engineer in me says this is a bad idea because of the potential for disaster,” Geller said. “But the practical, environmental side of me says it’s great. It’s just not for the faint of heart.”

With WVO, not all the oil combusts, he said, and over time carbon builds up in the engine and will damage it.

The problem is chemical not physical. “The molecules in the oil are big molecules, relatively speaking, compared to diesel molecules,” Geller said. “You can thin it all you want, but you aren’t changing the molecule structure.”

Geller has met hundreds of people who have used WVO in their vehicles for up to five years with no problems. He also knows some who have had unsuccessful ventures with WVO and other homemade fuel recipes.

“If you’re mindful of what you’re doing and are very mechanically inclined, go ahead and try it,” he said. “I wouldn’t personally do it.”

Geller has conducted numerous experiments with biodiesel, he said, and would use it in his own vehicle. “With biodiesel, you go to the pump, you put it in and you don’t have to think about it.”

WVO blended fuel is better for the environment, runs much cleaner than petroleum, is a renewable resource and relieves some of our dependence on foreign oil, he said. “But you can get all the same advantages from biodiesel, and you don’t have to make it yourself.”