Some tricks to oil the wheels of the fuel consumption test

Claimed consumption figures based on laboratory tests and not the real world


Cars may not be living up to their claimed fuel consumption, according to research.

Claimed fuel consumption figures are based on laboratory tests that are not only not representative of the real world but in which car manufacturers are allowed leeway between the tested vehicle and the one that takes to the road.

Methods used include stripping out weight, even down to leaving items like the spare wheel behind; taping the gaps between a car’s panels to improve aerodynamics; and disconnecting the alternator to reduce the drain on the engine’s performance – the test is short so no one will notice the battery is not charging. Other tricks include conducting the test at high-altitude tracks where the car runs more efficiently and pumping up the tyres to bursting to reduce their rolling resistance.

Despite the lack of reality of preparing a vehicle this way, such measures are still legal under EU and US fuel-testing systems.

“The reason motorists don’t see fuel economy claims translate into reality is that car makers are gaming the vehicle testing system,” according to James Nix, of An Taisce – the National Trust for Ireland, adding that “it’s an easy system to manipulate because manufacturers do things during the fuel cycle test that drivers would never do. They are not breaking any rules; the loopholes loom so large that car manufacturers can massage fuel economy results without being in formal breach of EU rules.”

Car makers say they are simply getting the best out of the car allowed by the test.

A proposed New European Driving Cycle test should eliminate many if not all of these loopholes, as well as providing a more realistic real-world estimation of fuel consumption. However its implementation is being resisted because it will drive up CO2 emissions figures and that is a financial no-no for the car makers.