For years no one took the U.S. Environmental Protection Agency's mileage stickers seriously. Then, in 2008, new procedures made these estimates seem at least reasonably in the ballpark for really cautious drivers.
Few knew, however, that the EPA did not perform these tests but rather accepted the manufacturers' estimates. But the mileage stickers on new cars say "EPA Fuel Economy Estimates," not "manufacturer's estimate."
I would be interested to learn what "procedural errors" by Hyundai and Kia caused them to overstate gas mileage. Oddly, the errors always favor the companies.