Every two or three weeks, Cole visits a North Waco chicken joint and empties out a 50-gallon oil barrel. He takes the free fuel home and filters it through a homemade system of pipes and barrels. Then he pumps it into a tank in the bed of his 1995 Ford F-350. The four-door truck, which can switch easily from diesel to cooking oil, is the only vehicle for his family of four.
"We take it on a lot of weekend trips down to Austin," he said. "Last week, we went to Victoria. The highway is where you get the most use out of your vegetable oil."
Cole, 26, farm manager at the nonprofit World Hunger Relief Inc. in Elm Mott, is one of a new breed of grease monkeys who are bucking high fuel prices through used vegetable oil.
Their motives are a blend of frugality, environmental altruism and good old do-it-yourself spirit.
"We were looking to buy a new vehicle 2 1/2 years ago," Cole said. "I wanted to buy a used truck, but I was learning about the environmental repercussions of our oil use and how it affects Third World people. ... I got sucked into the world of vegetable oil. I was totally fascinated by it. I bought the truck in spring of 2007, and I've been running it on vegetable oil for six months."
For Cole, it's also about avoiding the high cost of diesel -- which topped $4.50 a gallon at some Waco stations within the last week.
Waste vegetable oil is free or dirt-cheap if you don't mind getting your hands dirty and you're willing to spend the time and money to convert your engine. Cole bought a conversion kit for about $2,500, and he improvised a filtration system for about $250.
John Hendrickson, manager of Waco Transit, is holding the cost down on his diesel-to-waste oil conversion by using off-the-shelf parts designed for hot rods.
He estimates he will finish the conversion soon at a cost of about $1,500.
Hendrickson, 36, has been brewing his own biodiesel for a couple of years, using waste oil that he picks up from a convenience store fry pit. Biodiesel can run in a diesel engine without conversion.
But it requires methanol, an alcohol that has been getting expensive lately, so Hendrickson decided to switch to waste vegetable oil.
"I'm a cheap guy," he said. "I may end up using both biodiesel and waste oil."
He estimates that the cost of collecting the oil and purifying by running it through a centrifuge costs him 11 cents per gallon. He expects he will get 20 miles to the gallon on waste vegetable oil, slightly less than real diesel.
At prices like that, why doesn't everyone run on waste vegetable oil?
To begin with, it's a challenging fuel to use. At colder temperatures, it begins to gum up and can damage engines. Grease users like Cole and Hendrickson solve that problem by preheating the oil and starting and ending each trip with diesel to purge the system.
Then there's the question of supply.
In past years, restaurants have paid to have contractors pick up waste oil and were all too happy to give it away for free. Those days are coming to an end along with the era of cheap fuel, said Sammy Citrano, owner of George's Restaurant in Waco. In the past two years, he said, restaurants are starting to charge for their waste oil, and he has heard reports of people stealing the stuff from alleys.
"It's almost like copper," he said.
It's not that running diesel engines on waste vegetable oil is a new idea.
Rudolf Diesel himself experimented with using peanut oil in the engine that he invented, and in 1912 he pronounced it a potential rival to petroleum as a fuel. The oil crisis of the 1970s inspired some do-it-yourselfers to try vegetable oil, new or used.
One was David Tinsley, who used to own a chain of 50 Tinsley's Chicken restaurants and now owns Health Camp Burgers on the Circle in Waco.
In 1980, Tinsley started using leftover cottonseed oil from the chicken vats to fuel his Mercedes Benz turbodiesel sedan.
"I did 50-50 oil and diesel," said Tinsley, who lives near Lott. "It drove real good as long as it was warm weather. In a cold snap, it couldn't go over 15 or 20 miles an hour."
Tinsley still has the Mercedes, and he plans to start using grease in it again.
"I hate to throw anything away, because anything worth throwing away will someday fuel something," he said.
Another pioneer in the field is Max Shauck, a Baylor University aviation and mathematics professor.
After the oil shortages of the early 1970s, he began experimenting and running vehicles with biofuels that included waste vegetable oil. Currently, he is consulting with the airline industry and the Federal Aviation Administration on biofuel for jets.
"Giving the run-up on prices, everyone's desperate for a solution," he said. "When you look at (petroleum) oil at $137 a barrel, it's going to take everything we've got."
Shauck foresees large-scale biofuel production from crops such as algae, but he thinks the automotive use of waste vegetable oil will remain a niche market.
"For pure vegetable oil, I don't think it will be more than a very limited usage," he said. "It's going to be more for people who are interested in sustainable fuel."
Shauck said waste vegetable oil and similar biofuels don't emit sulfur pollutants, unlike diesel, but they can emit smog-forming nitrogen oxides.
While plant-based fuels emit the global warming gas carbon dioxide when burned, they are made from plants that actually take carbon from the air. So the carbon footprint is smaller than fossil fuels.
Both Hendrickson and Cole have come to see the societal benefits of biofuels over the years.
Hendrickson started working at his dad's automotive shop in Amarillo before he could drive, learning to customize buses. He got a job as a mechanic at the Lubbock public transit bus barn while he attended Texas Tech University for a business management degree. That allowed him to get into transit administration without losing his hands-on knowledge of engines.
Along the way, Hendrickson served as a soldier during the Gulf War era and came to see alternative energy is a strike against oil-rich regimes that fund terrorism.
"The more energy-independent we are, the better off we're going to be. We've got to take the money out of it."
Cole, a Richardson, Texas, native, studied agronomy at Texas A&M University. He shifted his career goal away from turf management to crop science after his encounter with a missionary from Senegal opened his eyes to world hunger.
"I thought, 'Why am I studying landscaping when I don't have a passion for it?' " he said. "I felt called to serve overseas long-term. Our goal is to do that in the next few years.
Cole said he hopes this summer to experiment with converting an old John Deere tractor at World Hunger Relief to run on waste vegetable oil.
The nonprofit Christian ministry trains interns to help the poor in areas such as Haiti, Africa and Bangladesh to develop low-tech innovations and sustainable agriculture methods.
Cole said he hopes his knowledge of vegetable oil fuel can someday help a struggling farmer overseas.
"I'm hoping this is something God has given me an interest for that I can use in the future," he said.