The most fuel-efficient automakers in America

Mazda's cars are the most fuel efficient on American roads and they spew the fewest pollutants, according to a pair of new federal reports. And it looks like it's going to stay that way.

In 2014, the company's adjusted fuel economy was 29.4 miles per gallon, best of any automaker. It's an accomplishment in and of itself, but even more notable because Mazda has no hybrid or electric models in its lineup. Year over year, Mazda's fuel economy improved by 1.3 mpg. Only BMW had a better year-over-year improvement at 1.9 MPG. Overall, the nation's fuel economy stagnated year over year.

Asian automakers dominated this year's list of most efficient automakers, which was included in the annual "Fuel Economy Trends" report issued by the Environmental Protection Agency on Wednesday.

Though numbers for 2015 are only preliminary Mazda is projected to retain its fuel-efficiency title the next time around. The company, with US operations based in Irvine, California, may break new ground, when the '15 numbers are finalized. Its vehicles are expected to average 30.1 MPG for the year, and the company will be the first manufacturer to break the 30-MPG threshold. When it comes to CO2 emissions, the company's cars average 302 grams per mile in 2014, and that's expected to improve by 6 grams per mile in 2015 data. Both are industry-leading figures.

On the flip side, Detroit's Big Three lead the list of most thirsty vehicles. It's important to remember the Big Three's immensely popular pickup trucks are an albatross of sorts in the EPA's evaluation, as they drag down the manufacturer averages. This is something some smaller automakers like Mazda don't need to worry about.

It's perhaps also important to remember the numbers are a snapshot of where the automakers essentially were a year ago, not where they're headed. Ford may languish near the bottom in this report, but Christopher Grundler, director of the EPA's Office of Transportation and Air Quality singled out the company for its responsiveness in pursuing improvements in light of tightening government standards.

Grundler said the light-weighted aluminum F-150 pickup was outperforming its targets by such a wide margin it was already meeting 2019 standards. One iteration of the popular pickup that contains a 2.7-liter EcoBoost engine is already meeting 2024 federal standards. "Our policy is creating incentives for carmakers to invest and bring (technology) forward faster than they ordinarily would," he said. The Ford F-150 is "an amazing story of innovation, and if you do regulation right, this is what you can achieve."

More broadly, Grundler pointed toward Ford's announcement that it would invest $4.5 billion in electric cars over the next five years to bring 13 new EVs to the market as another sign the automaker had been adept in mixing tightening standards with new technology. "Ford is not only saying the right things, they're putting money where their mouth is," he said.

Click on the image above to see where all the rest of the major automakers selling vehicles in America fall into place behind Mazda.