Mitsubishi Motors has admitted to rigging the official fuel economy tests of Japan for some of their Kei cars since June 2013. The affected models are the eK Wagon and eK Space. The Nissan Dayz and Dayz Roox, which are manufactured by Mitsubishi and supplied to Nissan, are also affected.

According to the press release, Mitsubishi “conducted testing improperly to present better fuel consumption rates than the actual rates; and that the testing method was also different from the one required by Japanese law. We express deep apologies to all of our customers and stakeholders for this issue“.

Around 157,000 models of the eK Wagon and eK Space and 468,000 models of Nissan’s Dayz and Dayz Roox have been rigged and both Mitsubishi and Nissan issued a stop-sale regarding the affected models, with the two companies now discussing about the compensation to be offered.

Sources online pointed out that it was Nissan who found deviations in the figures when they did their testing for the next generation models. It then requested from Mitsubishi to review the running resistance value (a combination of the rolling resistance and air resistance while on the move) that was set by the latter, causing an internal investigation. The wrong value used gave the cars better fuel economy figures than it should been.

It is also rumored that other models in Japan might have rigged figures too and they are now looking at whether other models sold outside of Japan have wrong economy numbers also.