Mitsubishi falsified fuel economy data for 25 years — and lost its independence

In April 2016, Mitsubishi Motors admitted that it had been falsifying fuel economy test data for at least 25 years, affecting approximately 625,000 vehicles sold in Japan. The company had used improper testing methods that produced more favorable fuel efficiency results than the cars actually achieved.

The admission came after Nissan, which had partnered with Mitsubishi on some of the affected models, discovered discrepancies in the data and pressed Mitsubishi for an explanation. Mitsubishi's stock fell 40% in the days following the admission, wiping out approximately $3 billion in market value.

The scandal led to Nissan acquiring a 34% controlling stake in Mitsubishi Motors, effectively ending Mitsubishi's independence as an automaker. The case illustrated how a culture of data manipulation can persist for decades when internal controls are weak, and how a single partner's due diligence can expose what internal audits missed for a quarter century.