Why the government won’t tell you which automaker had the most efficient 2013 models

In an industry that fights for every last sale, claiming the title for being the most fuel-efficient automaker in the country has traditionally been a huge win. Even in times like these when gas prices have eased, shoppers often compare mileages as much as horsepower, and when gas prices soar — as they inevitably will — having that message at the ready gets more tire-kickers into dealerships.

In the United States, it's a federal report that typically determines which automaker may call itself the most fuel-efficient. Yet this year, the U.S. Environmental Protection Agency went out of its way to deny that accolade to the automaker with the highest average efficiency from vehicles it sold in the 2013 model year: Hyundai.

The South Korean automaker has itself partly to blame: After touting its fuel efficiency for years, the company admitted in November 2012 that it had incorrectly measured the fuel economy of 900,000 Hyundais and Kias, forcing it to write down the MPG values on 13 models. That sparked an ongoing EPA investigation into how automakers report mileages, since the EPA often checks only a fraction of the figures they estimate; the flaw that forced Ford to perform a similar reduction on the C-Max Hybrid.

Hyundai and Kia's corrected data has been accepted by the EPA and worked into its annual report on fuel economy, including its proclamation that the fuel efficiency of new U.S. cars and trucks has never been higher, averaging an estimated 24 mpg for 2013 models. But when the EPA released its breakdown of average efficiency by automakers, it didn't include Hyundai and Kia in the published table, citing the open investigation — choosing to give top marks to Mazda and Honda instead.

Here's the real list of 2013 fuel efficiency, drawn from the EPA's own data and automaker's sales estimates. This compares top-level makes that sold at least 40,000 vehicles, so for example Volkswagen includes Audi: