The Greenest—and Meanest—Car Companies

The 2009 Honda Fit is unveiled at the New York International Auto Show in New York City.

Carmakers sure love the environment—like, all of a sudden. General Motors boasts that it has a dozen fuel-sipping models with highway gas mileage of 30 miles per gallon or higher. GM, Toyota, and Nissan are elbowing one another aside in a race to build an electric plug-in car with low or no emissions. And the automakers sound downright weepy when they describe future hydrogen-powered cars that emit nothing but water.

So who's really leading the way? There are different ways to measure which automakers are greenest, but one of the most straightforward is the combined gas mileage for all the cars in each manufacturer's fleet. As it turns out, the National Highway Transportation Safety Administration, which is responsible for implementing aggressive new fuel economy standards, recently published data supplied by the automakers on their planned fleetwide fuel economy for 2011, the first year the new gas-mileage standards go into effect.

While 2011 is still three years away, the complexities of designing and manufacturing automobiles require product plans to be more or less finalized several years in advance. So the models each company plans to offer in 2011 are pretty much locked in. The automakers can still mix and match components like engines and transmissions—which they'll probably have to do in order to meet the new mileage requirements. But the 2011 figures remain a good indicator of who will have the most and least efficient fleets. What the numbers show:

Japan trumps Detroit. This familiar storyline still holds true, despite improvements by the domestic automakers. Honda, Toyota, and Nissan will all turn out passenger car fleets with above-average gas mileage in 2011, while GM, Ford, and Chrysler will fall below the average. And the gap between Honda, at the top, and GM, toward the bottom, is a hefty 23 percent. The rankings reflect the success the Japanese automakers have had with small cars like the Toyota Corolla, Honda Fit, and Nissan Sentra—and with hybrids like the Toyota Prius and Honda Civic—just when Americans want them most.

Efficient cars but poor numbers. Volkswagen and Subaru have relatively low fleetwide averages for cars, even though their vehicles get relatively good mileage. That's because they build fewer models than bigger competitors, especially among tiny subcompacts that tend to get the best mileage. They may consider introducing more such models to help raise their overall mpg average.

The gap is closer on trucks and SUVs. In the light truck category, which the government considers distinct from passenger cars, the gap between Detroit and Japan is much smaller—and, in fact, almost inconsequential. Toyota's light truck mpg number, for example, is just 2 percent better than GM's—and lower than Ford's or Chrysler's. Honda ranks higher, but that's largely because it doesn't offer a big pickup truck. Neither do the top three in the category—Subaru, Mitsubishi, and Hyundai—which mainly sell small- and medium-sized crossovers.

Luxury makes finish last. It's no surprise that Porsche, Mercedes, and BMW rank near the bottom, since most of their customers seek performance rather than fuel efficiency. But that may be changing as gas prices crest $4 per gallon. In one recent survey, 27 percent of the wealthiest consumers said the price of gas affected the kind of car they bought. That's up from a meager 2.6 percent just three years ago. A Porsche hybrid, anyone?

Note: Data represent "adjusted baseline" mpg figures as computed by the National Highway Traffic Safety Administration, which account for certain manufacturers making minor technological changes to meet government requirements.