Mercedes are the current leaders at manipulating the way vehicles are tested, producing official fuel economy figures around 40% better than those that can be achieved in the real world according to the Transport & Environment’s (T&E) 2014 Mind the Gap report.
On average, across all car brands, the gap between real-world fuel consumption and carmakers’ claims has widened from 8% in 2001 to a staggering 31% in 2013 for private motorists; the gap for company car drivers averages 43%.
The obsolete test is unrepresentative of modern cars and is full of loopholes that carmakers exploit to produce better test results. Carmakers produce specially prepared prototype vehicles and pay testing services that help to optimise the results. Modern engine management systems are even able to detect when a test is being carried out to deliver better fuel-efficiency results – a technique known as ‘cycle beating’ that was first used to cheat tests for air pollution.
A new, more realistic and robust global test, the WLTP, is scheduled to be introduced in 2017, but EU countries are under pressure from carmakers that want to be able to keep exploiting the loopholes in the current test rules until at least 2022.
The growing gap between test and real-world performance is also damaging EU growth and climate goals. T&E forecasts that without the new test the average gap will grow to more than 50% by 2020. US authorities have been far more effective in identifying carmakers unfairly distorting tests. Hyundai and Ford have been required to reimburse customers for incorrect fuel economy figures while Mercedes and BMW-Mini are awaiting sanctions.