The Hyundai Kia Automotive Group is apologizing in the U.S. for inflating the gas mileage of some of its cars sold in North America.

In a full page ad in the Washington Post on Sunday, the carmaker acknowledged an error in overstating the gas mileage on roughly 900-thousand vehicles sold over the past two years in the U.S. and offered a sincere apology.

Hyundai Kia said it places top priority on making things right for the customer and it will lower gas mileage ratings on the models in question by an average three percent.

The U.S. Environmental Protection Agency discovered the bloated ratings during a recent audit, and Hyundai Kia has responded saying it will revamp its gas mileage test process and compensate car owners for the difference in mileage.