What Car? True MPG winners and losers

• Cars that fall short of MPG figures…
• …and those that hit the mark
• What's your True MPG?

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Driving a Kia Picanto could be a lot more costly than you think, while Mercedes-Benz S350L CDI Bluetec owners should be paying less than expected to keep their car moving, according to real-world fuel efficiency figures from What Car?'s new True MPG service.

What Car? True MPG economy testing programme has revealed the cars that live up to and fall short of official Government figures when driven in real-world conditions on the UK's road network.

Official mpg figures are controlled by EU law and are conducted in laboratory conditions on rolling roads. However, What Car?'s True MPG takes the test to the UK's streets and uses real-world driving data to provide a powerful tool to help buyers choose the car that's right for them – and their driving habits.

The Kia Picanto 1.0 2 and Mercedes-Benz S350L CDI Bluetec reveal the stark benefits of using What Car?'s True MPG, with the Kia supermini failing to thrive in real-world driving conditions, while the Mercedes' eco-friendly Bluetec model exceeds its official MPG expectations.

Kia's popular supermini records a What Car? True MPG average economy of 41.2mpg in our real-world driving tests, which is much less than the official laboratory-based figure of 67.3mpg.

A Picanto owner driving an average of 12,000 miles per year could pay around £2200 more for fuel than official figures suggest over a period of three years.

For example, comparing the difference between official mpg figures and What Car? True MPG data, the difference in purchase price between a Ford Fiesta 1.25 82 Zetec and the Kia Picanto 1.0 2 – considering the additional expense of fuel over three years – could shrink from £2750 to just £1435.

Hybrid cars calculation
If you are thinking about buying a hybrid car you should also take time to visit What Car?'s True MPG site. A Peugeot 3008 Hybrid4 with an official average of 70mpg, was found by our testers to manage just 46mpg – a shortfall of 24 miles. This equates to a driver travelling 12,000 miles a year, spending an extra £1821 over a three-year period.

Drivers looking to profit from real-world driving costs revealed by the What Car? initiative could do worse than considering the Mercedes-Benz S350L CDI Bluetec. The S-Class exceeds official expectations for its average economy by 2%, which equates to a saving of £105 over three years for a motorist doing 12,000 miles a year. Small change for a car that costs £64,610, but the What Car? True MPG initiative will reveal other cars that closely match or exceed official mileage expectations.

The Vauxhall Corsa 1.2i VVT Ecoflex SXi S/S also performs well, with only -1% variance from its official average mpg figure. This is particularly impressive for the supermini, which sits among larger, more sophisticated cars at this end of the True MPG scale. Relate this to a three-year period with the driver covering 12,000 miles a year, and the Corsa will add just £53 to the cost of the official mpg expectations.

Find out for yourself
If you're buying a car, then make sure you visit the True MPG website to find the True MPG figure for the car you're considering – and on the roads you drive.

Pete Barden

*Price comparisons are based on the average price per litre of unleaded and diesel week ending April 27, 2012. Data sourced from fuel price data is supplied by Experian Catalist in cooperation with Arval UK Ltd.