Penny-pinching motorists are putting themselves to the test in the 400-mile 2008 MPG Marathon fuel-saving race from Bristol to Macclesfield and back.
The winner of the last two events, Peak Performance training firm boss James Sutherland, is confident of making it three in a row in a Toyota Aygo.
He said: "In 2007, we managed 79.4mpg against a combined figure of 61.4mpg in a 1.0 litre petrol Aygo. This year we will be pushing to top 80mpg, although the route is always challenging."
AA president Edmund King is driving a Fiat 500 1.3 Multijet that records and analyses information about driving styles, which helps to use less fuel.
Mr King said: "Despite fuel prices falling marginally in recent weeks, the cost of filling a car with fuel is still very high.
"Motorists up and down the country have felt the pinch, so the MPG Marathon is a timely reminder of how a few simple techniques can cut as much as 10% to 15% off the fuel bill.
"Such a saving could pay for a family holiday or even be put towards a new car. Either way, driving more economically can cut hundreds of pounds off the amount we pay for fuel each year."
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