South Korean car maker, Hyundai, will be reimbursing 900,000 vehicle owners for inaccurate mileage estimates on certain Hyundai and Kia vehicles sold in the last two years. The Environmental Protection Agency (EPA) began an investigation and discovered the discrepancy after consumer complaints that the estimated mileages were unachievable. The estimated mileage is the result of a government standardized test that all automobile manufacturers must follow to calculate mileage so buyers can more easily compare the fuel efficiency of various models.

Hyundai apologized for the inaccurate figures, saying they were the result of internal testing errors in the vehicles EPA certification. Customers will be reimbursed for the difference between the stated and actual gas mileage, and mileage estimates will be restated for the affected models. According to the E.P.A., this is the third time since 2000 that manufacturers were required to relabel a vehicle’s fuel economy.