MONTREAL - With gas prices on the rise, some motorists are turning to an unusual source -- the deep fryer -- to avoid paying big bucks at the pump.

One Montreal mechanic converts diesel vehicles to run on cooking oil that can be obtained from a restaurant, often at no charge.

"Since fuel prices went up, the phone started ringing off the hook,'' said Marc Amsden, owner of EcoAuto garage.

With some analysts predicting gas to hit $1.50 a litre across Canada, the former Volkswagen mechanic expects to have a busy summer.

Many of Amsden's customers haul big vehicles on long drives and, for them, the switch to vegetable oil means a big drop in costs.

But for Amsden, the main selling point of the converted tank is not the savings.

"To me it's not a fuel-price issue, to me it's a pollution issue,'' he said.

Amsden encourages his customers to use recycled vegetable oil rather than virgin oil derived from food crops.

"If you're taking new food stock to make this oil then we're not much more ahead,'' said Amsden.

Stuart Patterson, 51, bought a car from Amsden last fall.

Patterson used to own three cars _ one "hot'' car for summer, one for winter driving, and another to get to work. Now, he drives only a sedan with a converted fuel tank.

He uses it to make the daily commute, against traffic, between his home in downtown Montreal and his office in the suburbs.

"You can never go back to what you were doing before, because you realize how stupid it was _ how you were beholden to the oil companies,'' he said.

Patterson fills up his tank for a fraction of the price with recycled oil from Amsden's garage, a move which eases both his pocket book and conscience.

"A kid I work with, he drives 150 kilometres a day and he looks at this and thinks, this car could pay for itself in two years with the price of gas what it is.''

Running a car on recycled cooking oil rather than fossil fuels means a net reduction in carbon emissions, according to Don Smith, professor of plant sciences at McGill University and an expert on biofuels.

Smith said used cooking oil can be turned into soap and other products, but a lot of the time _ at least in the past _ it was thrown out.

"By using cooking oil you turn a waste stream into a resource stream,'' he said.

"It's not going to be a gigantic source (of fuel), but with that kind of thing it solves two problems, so we should do it.''

Amsden admits the engines aren't perfect. Running a car on vegetable oil can be difficult in the middle of a cold Canadian winter.

Vegetable oil freezes at a higher temperature than diesel or gas, at around -15 C, so motorists have to run their car on diesel until the vegetable oil heats up.

"When it gets very cold it's not really suggested you do it,'' Amsden said.

On long drives, it can be difficult to find a place to fill up on vegetable oil.

"Most people bring a couple of jerry cans or an extra barrel,'' Amsden said.

Patterson plans to drive to Nova Scotia this summer. Last year he asked the owner of a breakfast joint if he could use their oil.

"He said, `Sure, take it. We have to pay to get rid of it.'''