When Larry Casella, his son and a friend drove to Bozeman, Mont., on a recent fishing trip, they were traveling on a wing and a prayer and a good bit more: gallons of used vegetable grease, much of which he mooched from restaurants along the way.

"It was pretty much what we expected," Mr. Casella, a Mt. Lebanon attorney and lifelong car tinkerer, said of the 5,493-mile round trip in the grease-powered 1984 Mercedes-Benz station wagon. "But we had a few problems on a few things."

The car, which he bought on eBay, has a regular petro- diesel engine retrofitted with a 15-gallon system that allows it to run on processed waste vegetable oil. The battleship-gray Mercedes can't run on leftover Crisco alone, however, because vegetable oil must be heated before it thins enough to work through the fuel line.

That means regular diesel is used to start the car and to serve as backup if the supply of vegetable oil runs out or if there are glitches in Mr. Casella's still-experimental system.

Waste vegetable oil fuel is often home-brewed, and, although, there are any number of Web sites and manuals offering help, making fuel is an iffy science.

Ken Valerio, a retired firefighter from Erie and the friend who went along on the trip, made the fuel. "His brother owns five restaurants so he can get the grease," Mr. Casella said.

It was up to the third traveler, Mr. Casella's son, Anthony, a Mt. Lebanon High School senior, to figure out the best way of storing the grease. Removing one passenger seat allowed them to pack 10 containers of oil in addition to their luggage and camping gear.

Anthony, a journal for the trip, and his Zune MP3 player had to wedge into the back as well.

"You couldn't fit a candy bar in there," Mr. Casella said, leaning into the interior of a car still smelling faintly of fast-food takeout.

"You couldn't see out the back at all. I guess that's not legal," he added, smiling.

Running an engine on fossil-free fuel is hardly a novel idea. Dr. Rudolf Diesel displayed an engine that ran on peanut oil in the late 1800s, and various forms were popular in the early 20th century.

But the cheap availability of fossil fuels made regular gasoline and petrodiesel the American fuel of choice.

"There's a common knowledge that you can run a car on vegetable oil," said Dave Rosenstraus, president of Fossil Free Fuels in Braddock, which not only sells and installs converter kits, but also processes and sells vegetable oil fuel.

People often confuse waste vegetable oil with biodiesel, which is often a graded mix of petro and vegetable oils. Biodiesel is a fuel of choice in Europe, but still scarce at the pump in this country.

Mr. Casella's foray into alternative fuels began last winter, when Mr. Valerio got him interested.

"I don't have the desire or the capacity to process vegetable oil, so I was kind of looking for a conversion kit," he said.

He browsed eBay, finally settling on the Mercedes.

"The car cost $4,500, and that was probably above market value, but the owner was selling it with two filter pumps and the [conversion] kit. I calculate we got about $2,500 in extra stuff, so in my mind, I paid $2,000," Mr. Casella said.

He took the car to Fossil Free Fuels for a checkup -- "If I hadn't had this system already, I would have bought theirs" -- and began planning the fishing trip.

The idea was to stock up on 5-gallon, plastic fuel containers of vegetable oil, and when that ran out, mooch the rest.

Unanswered cries

He ordered two magnetic signs, one for each side of the car. In black type on a white background, the signs read: "We need used fryer oil. Call or text [their cell number, which Mr. Casella referred to as 'the grease phone.']"

"My son and friend think [the signs are] corny, but I thought they would work," he said.

"I wasn't as confident about it as my dad was," admitted Anthony, shaking his head.

White lettering along the back windshield of the car also reads "Powered by vegetable oil."

Alas, the signs attracted attention at rest stops but no one called. "Maybe they thought it was an office number," Mr. Casella said. "But people were taking pictures everywhere. We ran into this British guy, twice, on different parts of the river.

"At this one truck stop, there was this guy hauling pigs. We said 'We're going to Montana on vegetable oil' and he said 'Okaaaaay.' "

It isn't possible to just drive up to a restaurant's grease trap and begin transferring the oil. It has to be filtered first, a long, messy process.

At a restaurant in LaSalle, Ill., it took about an hour to filter 20 gallons of oil.

"It was a four-star restaurant owned by a man from Macedonia, so we called that our 'Macedonian oil,' " Mr. Casella said. "When we filtered [the] oil, there were french fries and stuff floating in it. The one end of the filter got clogged; we used Anthony's toothbrush to clean it off.

"Of course, then we bought Anthony a new toothbrush."

Some restaurants don't care who takes the used grease, which is often just stored out back near the trash.

Others make deals with biofuel processors, so that oil is already spoken for. Even if deals aren't made, locals have staked their claims.

"You'd get to some restaurants and they'd say you could take the grease, but there would be containers out there with names and telephone numbers on the jugs, so we didn't take it," Mr. Casella said.

Other times, rainwater had seeped into the containers. It would take days to get it out. "The rain gets in and that's like a death knell," he said. "We won't use those."

The trio took a laptop with them and scoured the Web to find places that claimed to offer free waste vegetable oil or listed places to buy it.

In Idaho, Mr. Casella e-mailed Paul House, owner of Bozeman Biofuels and arranged to buy 35 gallons of filtered WVO of better quality than what they started out with in Pittsburgh.

Smelling like fries

"We went about 850 miles on his grease, although it's kind of hard to tell how many gallons you're getting because you're using either tank," he said.

The trip wasn't without a few hitches unrelated to the workings of the car.

"When we were camping, we heard there were grizzly sightings," Mr. Casella said. "I was concerned because we were smelling like fried chicken and sleeping outside."

Also, the fishing wasn't the best.

More troublesome was a problem with the car; it would suddenly lose power.

"We had a lot of theories and spent a lot of time experimenting," he said. "Trouble is, you think everything is all right and drive 50 miles and then start losing power again."

Everything -- from the vegetable oil cooling off on the way to the engine to faulty oil filters, or even that the original oil wasn't properly filtered -- was considered.

"After we used the oil from Mt. Lebanon, we probably used two tanks of diesel. We didn't want to think that the filters were getting dirty so quickly."

Mr. Casella brought along five oil filters, figuring he'd have to make one change.

Instead, for a while they were changing the filter after 600 miles, constantly hauling out the big leather satchel stuffed with car manuals and Internet printouts.

So it isn't a perfect system.

Growing up, Mr. Casella said, "I was just a kid without a lot of money who liked to work on cheap cars," and he admitted that this latest project was more from a love of tinkering with old cars than from trying to save the planet from toxic fuel emissions.

"That's another reason I'm glad Anthony came with us," said Mr. Casella, whose wife, Penelope, and daughter, Nina, prefer the family's other car, a dark-red Saturn.

"As a kid, I used to work on cars, so I was used to it. But kids today have computers and video games, and this is the sort of thing where you're getting your hands dirty."

Summer's far from over, and trips are being considered to, appropriately, the National Buffalo Wing Festival during Labor Day weekend -- plenty of grease there -- and Cape Cod.

Driving the Mercedes is a kind of a work in progress, one Mr. Casella said he's enjoying.

"It does get 24 miles to the gallon, and it's a pretty big engine. We plan on keeping this one for the duration."