Mitsubishi Motors Corp used fuel economy testing methods that were not compliant with Japanese regulations since 1991 – much longer than previously known, a source briefed on the matter said.
Japan’s sixth-largest automaker has lost half of its market value – some $3.9 billion – since it admitted last week that it overstated the fuel economy of four domestic minivehicle models, including two produced for Nissan Motor Co.
The automaker has also said it used testing methods that were not compliant with Japanese standards going back to at least 2002.
The source declined to be identified due to the sensitivity of the issue.
The news was first reported by the Nikkei business daily. A Mitsubishi spokesman declined to comment. The company plans to hold a briefing later in the day.
Mitsubishi has said that it had been compiling data for fuel economy tests using U.S. standards, where higher-speed, highway driving is common, rather than Japanese standards, which are set to reflect city driving, whose stop-and-go conditions tend to use more fuel.
The transport ministry on Tuesday announced it had set up a task force to examine how other automakers submit fuel economy data.
The revelations have sparked fears of ballooning compensation costs and fines and prompted Japanese authorities to raid one of its research and development facilities.
Standard & Poor’s has also warned the automaker’s rating could be lowered further into speculative grade territory.