Car brands ‘manipulate MPG tests’ by up to 25 per cent to make cars appear more fuel-efficient and eco-friendly

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Published: 15 March 2013

The revelation that car manufacturers are willingly manipulating MPG tests to inflate fuel efficiency and help sell cars is hardly surprising.

A new report by the Transport and Environment campaign group outlines the ways manufacturers are said to ‘cheat’ the system and get away with advertising incorrectly high fuel economies.

Some models even emit 50 per cent more emissions than advertised in test results. The growing gaps are leading drivers to become distrustful of official data on fuel economy, making them less likely to consider buying a more fuel efficient vehicle, the campaign groups says.

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Most drivers find it impossible to achieve the advertised fuel economy of their vehicles. “The large and growing gap between official fuel test results and average real-world driving is not caused by the way cars are used and driven,” the report explained, “but because the official test is totally unrepresentative of typical driving and the results are being lowered by manipulating testing procedures.”

The report alleges that ‘testing and checks on production vehicles are inconsistent and inadequate, with manufacturers paying the organisations undertaking and certifying the tests’.

And while there is no firm evidence to suggest car makers are breaking any formal rules, the current test procedures are ‘so lax there is ample opportunity to massage the test results’.

From taping over protrusions in the body to reduce aerodynamic drag, using high-end, expensive lubricants for the car parts, altering wheel alignment to reduce rolling resistance, fitting special tyres with a lower resistance and overinflating them to make them even more efficient, the report says manufacturers spend countless hours thinking up measures on how they can make the fuel economy as eco-friendly as possible - at least on appearance.

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The Society of Motor Manufacturers and Traders Limited said: “All vehicle manufacturers follow standardised test procedures for mpg and CO2 as set out by European law.

“As an industry we support enhancements to the test procedures and are contributing to the development of a new test cycle – a detailed process that aims to align worldwide testing procedures.

“The new test is designed to better represent real-world driving, but as all motorists know vehicle performance depends on a range of factors including driving style, maintenance standards, climatic conditions and loads carried.

“Testing a limited number of vehicles is prone to error. 2012 government data shows that vehicle manufacturers carried out more than 3,500 independently verified tests in accordance with detailed legal guidelines set out by the European Commission.

“Each model of the vehicles tested received an initial test, which is followed by random monitoring of the same types of vehicle as they leave the production line, taking the overall test numbers into the tens of thousands.

“This process ensures repeatability, conformity and eradicates anomalies that can occur by testing a very small sample of models.”