Nine Mitsubishi models currently on sale in Japan have incorrect fuel economy ratings, the automaker admitted in an update to Japan's Ministry of Land, Infrastructure, Transport and Tourism (MLIT).
In a statement released overnight, Mitsubishi Motors stated "running resistance was improperly calculated in nine other models currently sold in Japan, as well as in other models no longer sold in Japan".
By our calculations, only nine models in Mitsubishi's domestic market lineup are designed and produced in-house, the remainder are restyled and rebadged models built by other car makers, including Suzuki and Nissan.
The automaker suspects that "desktop calculations" were also used in the fuel economy numbers of other models, including the RVR, which is sold in Australia as the ASX. The company is still investigating whether it published improperly derived economy figures in overseas markets.
Above: The Nissan Dayz Roox is based on the Mitsubishi eK Space, and built by Mitusbishi.
After news broke in late April that it had improperly calculated the domestic fuel economy numbers since 1991, the United States' Environmental Protection Agency ordered Mitsubishi to investigate its US mileage numbers and recalculate its coast down tests.
Within days Mitsubishi's American arm responded: "After a thorough review of all 2013MY to 2017MY vehicles sold in the United States, we have determined that none of these vehicles are affected. Our findings confirm that fuel economy testing data for these U.S. market vehicles is accurate and complies with established EPA procedures."
In its latest submission to MLIT, Mitsubishi has detailed some of its findings into why and how it doctored figures for the eK, eK Space, Nissan Dayz, and Nissan Dayz Roox kei cars.
According to the company, it used running resistance data from the eco-minded variants of the eK and Dayz to generate fuel economy numbers for other models in the range, including the standard, turbo and 4WD grades.
Above: Mitsubishi eK.
Additionally, during the development cycle the fuel consumption target for these cars was lowered five times by executives and managers, from 3.8L/100km to 3.4L/100km.
Engineers repotedly knew that "fuel consumption meant 'the factor that would give the most product marketing appeal'" and believed that the targets were "absolute".
Acknowledging the problems above, Mitsubishi says that "drastic reforms are being considered in order to prevent recurrence".