A group of British eco-enthusiasts have just pulled off the greenest and grubbiest car rally ever, driving from London to Athens in vehicles powered exclusively on waste vegetable oil.

The team motored with unexpected ease across Europe on the proceeds of the grease thrown away by restaurants and cafes along the way. Their hope is that the 2,500-mile feat will help a drive to create a commodity out of cooking oils that otherwise end up in landfills or the sea. Unlike ethanol and other controversial biofuels, recycled cooking fat does not impact on food production.

"I think we can safely say that this is the first long-distance car journey in Europe that has relied on restaurants and burger bars as an informal network of filling stations," said Andy Pag, a 34-year-old Londoner, who organised the rally.

"It's true we spent a lot of time fat-finding, knocking on the doors of restaurants begging for their waste, but it worked. And the beauty, of course, is that when such supplies are collected straight from a restaurant and used as fuel they have a zero-carbon footprint," he told the Guardian, after an awards ceremony highlighting alternatives to fossil fuels at the British embassy in Athens.

Eight teams took part, driving cars that ranged from a brand new Renault to, in Pag's case, a 13–year-old former taxi. They estimate that 350 litres of cooking oil were used to fuel the 11-day expedition.