Three-year-old cars released onto the used car market from tomorrow (September 1) will boost new owners’ fuel economy on average by 7%, saving them around £88 a year, says the AA.

A new plate change on Saturday will start the release of three-year-old cars coming up to their first MOT test onto the used-car market, their owners switching to a brand new model to avoid potential repair costs and inconvenience.

Department for Transport figures show that new petrol cars manufactured in 2009 averaged 42.7 miles per gallon, compared to 39.9 in 2008. With a UK car averaging 8,610 miles a year, the 7% fuel economy improvement saves 64 litres of fuel a year. With UK petrol currently averaging 138.36p a litre, the saving is worth £88.55.

Diesel cars built in 2009 (49.8 mpg) were, on average, 3.75% more fuel efficient than the year before (48.0 mpg) and 8.25% more frugal than 2007 models (46.0 mpg). This gives someone who owns a 2007 diesel car the potential to save an average of 65 litres a year, worth £92.92, by upgrading to a model built three years ago.

Edmund King, AA president, said: “People looking for a used car could cash in by doing some of research. If you are upgrading your car look for a newer model with better fuel efficiency, better reliability and hopefully a higher Euro NCAP safety rating. The fuel savings on an average newer model could actually save you the cost of your Vehicle Excise Duty. With a continued trend of high fuel prices it is well worth purchasing a more fuel efficient model.”