Mitsubishi Motors Corp., the Japanese automaker that acknowledged that it had intentionally lied about fuel economy data for some of its models, said an internal investigation found such tampering dated back to 1991.
The Wall Street Journal reported last week that Mitsubishi Motors employees improperly manipulated fuel-economy data to inflate mileage results on at least 625,000 vehicles,
President Tetsuro Aikawa told reporters the internal investigation was ongoing, suggesting that more irregularities might be found.
Aikawa said so much was unknown that it's uncertain what action the company will take. He said he didn't know why employees resorted to such tactics to make mileage look better.
The inaccurate mileage tests involved 157,000 of its eK wagon and eK Space light passenger cars, and 468,000 Dayz and Dayz Roox vehicles produced for Nissan Motor Co. The models are all so-called "minicars" with tiny engines whose main attraction is generally great mileage. They were produced from March 2013. The problem surfaced after Nissan pointed out inconsistencies in data.
The automaker found the company's mileage goal for the minicars that had been set in 2011 was suddenly raised in 2013. Why that happened is unclear, according to officials. Aikawa also said it was unclear how customers were going to be compensated because the extent of the cheating was still under investigation.
Mileage fraud is a violation of Japan's fuel efficiency law for autos because buyers are eligible for tax breaks if a vehicle model delivers good mileage. Possible penalties are still unclear due to the uncertainties over the investigation's outcome, according to the transport ministry.
Production and sales of all affected models have been halted.
Mitsubishi Motors struggled for years to win back consumer trust after an auto defects scandal in the early 2000s over cover-ups of problems such as failing brakes, faulty clutches and fuel tanks prone to falling off dating back to the 1970s. That resulted in more than a million vehicles being recalled retroactively.