What Car? has launched True MPG, an initiative designed to give Britain’s car buyers realistic fuel economy information.

Until now, consumers and dealers alike have had to rely on carmakers’ own figures, which are conducted in laboratory conditions on rolling roads.

In the vast majority of cases What Car?’s figures are significantly lower than the official listings.

Some of the biggest discrepancies are on the BMW 118d SE (62.8mpg to 47.2mpg), Ford Focus Estate 1.6 TDCi 115 Titanium (67.3mpg to 42.3mpg), Kia Picanto 1.0 2 (67.3mpg to 41.2mpg), Mini 1.6D Cooper (74.3mpg to 52.5mpg), Toyota Prius 1.8 VVT-i T Spirit pre-face-lift (70.6mpg to 52.2mpg) and Volkswagen Jetta 1.6 TDI 105 Bluemotion Technology S (67.3mpg to 48.4mpg).

The Mercedes-Benz S350L CDI Bluetec was unique in that What Car? achieved better consumption than the official figure, 37.3mpg compared to 36.7mpg.

What Car? editor-in-chief Chas Hallett commented: “True MPG will allow motorists to select a car personalised to their driving needs and budget. We hope that it will become invaluable in the complex and emotional car-buying process.”