How did Hyundai-Kia get its estimated mileage ratings so wrong that it had to offer reimbursement to some 900,000 owners? The truth is complicated, and it gets to the complexities of EPA testing.
Hyundai-Kia's Sung Hwan Cho told reporters this morning that it's "a very complex testing process." Cho heads the automaker's U.S. technical centers. He shed some light on the EPA tests, which lead to the city and highway fuel-economy figures on a new-car window sticker. A key part of the tests involve measuring the resistance of various systems, dubbed the "road load" by engineers: how a car's tires meet the pavement, how the vehicle's shape cuts through the air and how the drivetrain's moving parts work in tandem. Each area translates to fuel efficiency, or lack thereof.
"There are hundreds of different parameters that can affect this road load," Cho said. "Ambient temperature, wind speeds, atmospheric pressure."
Then there's a litany of variations within each test vehicle — how many miles are on it, the condition of the drivetrain, the tire wear. Finally, the test procedures themselves involve "which kind of regulation and guidance procedures you follow, and how you process the data, and how you calibrate your measurements," he said.
Somewhere in those variations, Hyundai-Kia went askew of EPA guidance. But exactly how much guidance exists is up in the air.