• Makers of gas-guzzling cars cheat emissions tests the most

    Car manufacturers that sell the majority of gas-guzzlers in Europe manipulate fuel economy figures in tests much more than those makers that produce more fuel-efficient vehicles, a new report by the International Council on Clean Transportation (ICCT) reveals. The report adds new evidence to a series of recent studies that show the gap between official test results and the fuel consumption drivers experience on the road is rapidly increasing year-on-year.

    The study compares, for the first time, the progress made by carmakers on official and real-world fuel consumption over the last ten years in Europe.

    Luxury car brand BMW captures top-spot, reporting fuel efficiency figures that are on average 30 % lower than in real-life. This means that a buyer of a typical BMW car will burn on average around a third more fuel than claimed in the brochure and on labels in dealerships.

    Audi ranks second with a ‘real v. claimed’ gap as wide as 28%, followed by Opel/Vauxhall (27%) and Mercedes (26%). At the bottom of the table, Toyota’s manipulation of emissions tests produces official fuel economy figures that are just 15% lower than the real-world performance of its vehicles, while Renault’s and Peugeot Citroën’s (PSA) figures are on average 16% lower.

    In 2005, the difference between reported and real-world fuel consumption for BMW was 12%. By 2011, this gap had more than doubled, rising to 30%. In comparison, Peugeot Citroën, producer of smaller vehicles, saw its gap increase from 12% to 16% over the same period. This suggests that the growing difference cannot be attributed to a change in driving style, but rather to further manipulation of test results by carmakers.

    On average, new cars’ official fuel efficiency figures are about 25% lower than their real-world fuel consumption. ICCT’s analysis also shows just 2% of German drivers matched the official fuel economy figures in 2011.

    Transport & Environment clean vehicles manager Greg Archer said: “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.” 

    Fig 1: Difference between manufacturers test results and average real-world driving in 2011 (derived from ICCT, 2013)

    Car manufacturers measure vehicle fuel consumption and CO2 emissions through a system of testing called the New European Driving Cycle (NEDC). This test cycle is out of date and unrepresentative and contains many loopholes that carmakers are increasingly exploiting to fiddle the official figures at the expense of consumers’ trust. A new global testing system, called World Light Duty Test Cycle and Procedures (WLTC/P), which will be finalised in 2014, is more robust and representative of real-world driving. The European Parliament and European Commission propose to introduce this improved test in 2017. This decision is currently being discussed among member states of the European Union.

    “The current test is over 30 years old and unrepresentative of real-world driving conditions. The lax testing rules allow carmakers to claim unachievable fuel economy. The European Commission and the European Parliament proposed to tackle this issue. EU member states should support them to ensure cheating of drivers stops,” Greg Archer concluded.


    • Link to diagram of different car test manipulations.