A fuel economy cheating scandal that began with a single line of microcars grew to encompass the entire domestic lineup of Mitsubishi Motors on Wednesday after the carmaker admitted it had published exaggerated mileage ratings for every model it sells in Japan.
Mitsubishi disclosed last month that it had been using improper methods to test fuel economy for 25 years. It admitted the mistake after engineers at another carmaker, Nissan, discovered discrepancies in the ratings of a family of ultralight cars developed by Mitsubishi and sold by both companies. Mitsubishi did not initially say how extensively it had used the unapproved methods, whether it was on all models or just a few.
On Wednesday, Mitsubishi added nine models — the remainder of its current lineup — to the list of affected vehicles. The company said it was still retesting older vehicles, but it said it had confirmed discrepancies in the ratings of an unspecified number of discontinued models too.
The company said it had even misstated the energy efficiency of a vehicle that does not use gasoline, the all-electric i-MiEV. It acknowledged that there could be problems with the ratings of every car and truck it had produced since 1991.
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“I think the fact that work was being done in an insular company was one big factor,” chairman Osamu Masuko said at a news conference.
He said successive Mitsubishi development teams had used the same flawed testing methods without questioning them, a failing he blamed on a closed corporate culture that discouraged employees from taking initiative or making waves.
“There was perhaps a sense that if someone authorized something in the past, it couldn’t be wrong,” he said.
Mitsubishi is already a diminished brand, especially in its home market, where its market share has shriveled since a scandal in the 2000s in which officials admitted hiding reports of dangerous vehicle defects for decades. Today, Mitsubishi’s favored markets are in countries like Southeast Asia and Russia. It sells only about 10 percent of its cars in Japan.
Analysts have speculated that Mitsubishi, a small manufacturer with far fewer resources than Nissan, promised its partner a car with impressive mileage specifications but was unable to deliver. Cheap, small-engine microcars are a fiercely competitive segment of the auto market in Japan, where they account for 40 percent of new cars sold. Fuel economy is one of their most crucial selling points.
Separately, Bloomberg News reported that Nissan may invest more than $1.84 billion in a play to take over Mitsubishi. According to the report first disclosed by Japanese broacaster NHK, Nissan is in the final stage of talks to effectively acquire Mitsubishi by taking a 34 percent stake.