According to Mitsubishi, the testing data for the US market vehicles complies with EPA procedures and a different method is used in the United States than Japan to gather fuel mileage figures – something the EPA calls "Road Load Coefficient," and the data is independently verified before submitting.
So far, the scandal seems to center on Japanese market cars, even if the findings date back to 1991.
Mitsubishi Motors North America Statement Regarding Fuel Consumption Testing Data
April 27, 2016
Mitsubishi Motors Corporation in Tokyo recently announced irregularities concerning fuel consumption testing data.
To confirm that U.S. market vehicles are not affected by this issue, Mitsubishi Motors R&D America, Inc., working together with Mitsubishi Motors Corporation, proactively conducted an internal audit of U.S. market vehicles going back several model years to check previously submitted data to the EPA. After a thorough review of all 2013MY – 2017MY vehicles sold in the United States, we have determined that none of these vehicles are affected. Our findings confirm that fuel economy testing data for these U.S. market vehicles is accurate and complies with established EPA procedures.
An entirely different system is used for the United States market to determine what the EPA calls Road Load Coefficient, strictly adhering to EPA procedures. The data generated is then independently verified for its accuracy before being submitted to the EPA for their fuel economy testing. MMNA has shared this information with EPA, California Air Resources Board and DOT.
Mitsubishi Motors Corporation has acted quickly to address this issue and is putting in place a committee of external experts to thoroughly and objectively continue this investigation. The results of the investigation, once completed, will be made public.
Mitsubishi Motors Corporation is also working closely with the Japanese Government to fully review the implications of this issue, and to discuss potential resolutions.