Mitsubishi fuel economy fix: not defeat device but running resistance

Mitsubishi Motors Corporation (MMC) has admitted to purposefully fabricating fuel consumption figures by misrepresenting the running resistance of four mini-car models: eK Wagon, eK Space, Dayz and Dayz Roox. The OEM said that the testing method it used to measure the running resistance of these models was “different from the one required by Japanese law,” and that it helped to provide “more advantageous fuel consumption rates than the actual rates.”

What is vehicle running resistance, and how is it usually tested?