Mitsubishi's eK Wagon, photo via Wikimedia.

Mitsubishi's eK Wagon, photo via Wikimedia. 

Mitsubishi Motors has admitted to inflating fuel-economy ratings for approximately 625,000 vehicles sold in the Japanese market, including the eK Wagon, eK Space, and Nissan's Dayz, which the automaker created for Nissan Motor.

An internal inquiry uncovered the fuel consumption cheat that was perpetuated by Nissan's questioning of the vehicles' fuel consumption data, according to NPR.

At a press conference on Wednesday, the Japanese automaker stated that employees improperly reduced tire running resistance on vehicles that were being tested for fuel efficiency.

The manipulation of the vehicles' fuel rating involved the way Mitsubishi calculated the effect of wind and tire resistance on the car during driving simulations, reports the New York Times. But the automaker admitted to secretly using a test method that can produce lower resistance and make the vehicle appear to be able to travel farther on less fuel.

Top Mitsubishi executives said they were not aware of the manipulation until it was pointed out by Nissan, the report went on to say.