Mitsubishi Motors Corp. used improper fuel economy data on more than 10 models that are no longer being sold in addition to the models already revealed, sources said Wednesday.
The automaker, engulfed in a fuel economy manipulation scandal since April, plans to report the findings to the Ministry of Land, Infrastructure, Transport and Tourism soon, the sources said.
The company's in-house investigation found that desktop calculations rather than actual test data were used to gauge fuel economy for the models, which it stopped selling over the past decade.
Among those vehicles, the automaker is alleged to have falsified data on several models that failed to meet fuel efficiency targets, the sources said.
Fuel economy is a key determining factor for customers partly because the government offers tax breaks for owners of eco-friendly cars.
Discrepancies with actual fuel economy data for the vehicles in question are likely to be hard to find because they are no longer on the market.
Mitsubishi Motors has already admitted to having manipulated data to make four minicar models — including two supplied to Nissan Motor Co. — look more efficient than they actually are. Their production was subsequently halted.
The automaker later revealed that desktop calculations were used for five more models.
The scandal has forced President Tetsuro Aikawa to announce his resignation to take the blame, damaged Mitsubishi Motors' brand image and caused sales to plunge.
The transport ministry had urged Mitsubishi Motors to check old data on vehicles that are no longer being sold to find any irregularities.