Japanese carmaker has lost half of its market value, $3.9bn, since it said fuel-economy readings were being falsified
The Japanese carmaker Mitsubishi Motors has admitted using fuel-economy testing methods that did not comply with Japanese regulations for 25 years, much longer than previously known.
It said on Tuesday that aggressive internal targets may have put pressure on employees to overstate the fuel economy of its vehicles, adding that it would set up an external committee to investigate the matter.
Japans sixth-largest carmaker has lost half its market value some $3.9bn (2.7bn) since it admitted last week to manipulating test data for four domestic mini-vehicle models, including two it produced for Nissan.
It has also said that more models may have used tests that did not comply with Japanese standards, prompting concern about ballooning potential compensation costs and fines. The US vehicle safety regulator is also seeking information, while Japanese authorities have raided one of the companys research and development facilities.
Mitsubishi said it used appropriate testing methods on vehicles sold in the United States, and had no indications of data manipulation in vehicles sold in other overseas markets.
It said it had been submitting non-compliant data to Japans transport ministry since 1991. It previously said such non-compliance went back only to at least 2002.
Ryugo Nakao, executive vice-president, said Japanese regulations changed in 1991 to require testing methods to better reflect stop-and-go urban driving, but Mitsubishi did not follow that rule change. We should have switched, but it turns out we didnt, he said.
A committee of external experts will report the results of its investigation in three months, he said.
Nakao added that repeatedly raised internal fuel-economy targets during the development of the affected models may have contributed to the cheating. Judging by what the investigations have shown so far, it seems there was pressure, he told reporters.
Another executive, Koji Yokomaku, said Mitsubishi Motors raised its fuel-economy targets five times in two years while developing the mini-vehicles, reaching 18.14 miles (29.2km) a litre from an initial target of 16.4 miles.