The Microjoule team managed the equivalent of 9,845 miles per gallon while driving for 10 miles around Silverstone race track in the UK.

Microjoule also won in 1998 with an average of 8,000 miles (12,800 kilometres) to the gallon.

Wacky races

The competition looked like the Wacky Races, but was serious stuff.

Charles Rhodes reports from Silverstone

More than 100 teams competed in the Shell Eco-Marathon. Their one goal was to see how far they can get these amazing machines to travel on a minuscule amount of fuel.

The big teams have backing from the car manufacturers

While we might be delirious if we managed 40 miles (64 kilometres) to the gallon (4.5 litres) pottering about town in our super minis, these people are not happy until they have seen the mileometer click through the thousands.

BBC News' Richard Bilton: last year's winner managed over 8,000 miles to the gallon

The teams have a choice of petrol or diesel, with solar assistance permitted for the first time this year. A car is allowed three 40-minute runs. It must average at least 15 mph (24 kph) after which the stewards at the meeting calculate the machine's fuel efficiency.

The vehicles get three 40 minute runs

"The top fuel teams do about 10 miles, which is six laps on the club circuit at Silverstone," says the event's fuel manager Geoff Houlbrook. "They do that on less than 10 millilitres which is just two teaspoons of fuel."

The entries come from all over Europe. Some teams use advanced materials like titanium and carbon fibre. Some of the machines built by schoolchildren are made from parts of old sewing and washing machines.

"It's fun but it's also science," says BBC Top Gear presenter and racing driver Tiff Needell. "It's like an experiment with people learning how to save energy."

Contestants have a day of practice before the event

Stewards measure the fuel to prevent cheating

The marathon draws all age groups

Solar assistance is allowed for the first time