Mitsubishi falsified fuel economy information on a pair of small cars it builds for its home market, the automaker said this week.

While the Japanese automaker isn't the first company to incorrectly self-report fuel economy for some of its products, what makes this situation unique is that a number of the cars were actually assembled under contract for Nissan.

The discrepancy was discovered by Nissan, which sells a version of the Mitsubishi eK as the Nissan Day. According to Bloomberg, the company admitted manipulating tire and air resistance to yield better fuel economy ratings. President Tetsuro Aikawa said the practice was "intentional." It is estimated that the affected cars overstate fuel economy by 5 to 10 percent. The company is now looking into who is responsible.

The eK and Day are microcars that qualify for Japan's tax-advantageous kei car class. The eK has been on sale in Japan for about five and a half years. A total of 620,000 cars sold over the last three years are involved.

Earlier today, Japanese officials raided one of the automaker's facilities. It remains unclear if other models will eventually be affected.

Japan's government calls the falsification "extremely serious."

Shares in the automaker have tumbled since news of the overstated fuel economy figures was released. As of this writing, the automaker has lost about a third of its market value. 

As automotive historians may recall, this isn't the first time Mitsubishi has come under close scrutiny. About 10 years ago, the automaker was investigated for covering up defective products and sweeping them under the rug for decades. 

Needless to say, it will be interesting to see how this scandal plays out against Volkswagen's "dieselgate" scandal.


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