Premium car manufacturers such as BMW are more able to manipulate fuel economy figures, new research has claimed.
A report produced by the International Council on Clean Transportation (ICCT) found that it was the premium car brands that were most likely to manipulate their fuel efficiency figures, reaching levels that real-world drivers would find difficult, if not impossible, to achieve.
Conversely, some of the more mainstream manufacturers were found to be the most honest with their statistics and offer results that its drivers could achieve on the open road, fleetworld.co.uk reports.
These results could prompt motorists to look into vehicle efficiency themselves - through car tracking systems - instead of relying on the manufacturers' claims alone.
It was BMW that was found to be the worst offender for real versus claimed fuel efficiency, with a difference of as much as 30 per cent. Audi came in second with 28 per cent, whilst Vauxhall (27 per cent) and Mercedes (26 per cent) followed.
Top of the class was Toyota, which only reported a 15 per cent difference between prescribed and real-world efficiency. Second place fell to Peugeot Citroen which just missed out after scoring 16 per cent.
A similar report undertaken in 2005 showed BMW's fuel efficiency difference was at just 12 per cent. By 2011 it had shot up to 30 per cent, where it has remained.
Commenting on the results, transport and environment clean vehicles manager Greg Archer told fleetnews.co.uk: "Car buyers in Europe need reliable fuel consumption figures to make informed purchase decisions. Carmakers aren't delivering. European politicians need to end the current manipulation of fuel economy data."