How CAFE Works: Fuel Economy and Corporate Politicking

By Jacob Brown | March 08, 2012
When someone mentions the government-mandated Corporate Average Fuel Economy program, with cars achieving 54.5 mpg by 2025, did you think the numbers were all from a straight average? Unfortunately, it's not that simple. Chances are likely most cars won't even get anywhere near 54.5 mpg in the next 13 years. While a car has to be more efficient than the vehicles of yore that maybe got 15 mpg if you were lucky, there's some gerrymandering involved, too. Each year, the Environmental Protection Agency weights CAFE based on the numbers of each kind of car produced in a given model year—not necessarily sold. They're split into domestic cars with parts mostly sourced in North America, foreign cars, and light trucks. The models are further broken down by "footprint," or the square-foot size they take up on the road. There are two classes for cars and two for light trucks, which include trucks, minivans, crossovers, SUVs, and some tall wagons like the Subaru Outback. Heavy duty vehicles with a loaded-up gross vehicle weight rating of more than 8,500 pounds are exempt from the averages.
Because a car's fuel efficiency can vary significantly between different engine and transmission options, it's more beneficial for an automaker to produce more miserly variants of a car. Take, for instance, that a 2012 Honda Civic Si sedan can achieve an EPA-rated 31 mpg on the highway. Yet, the Civic HF can get up to 41 mpg. A hybrid system can bump that up even higher. CAFE and the EPA aren't without their share of controversy, though. The number you see on a window sticker is not the same as that used by CAFE. CAFE numbers are generally higher, and they give an incentive for building more alternative-fuel cars like hybrids and electric vehicles. This was a major point of contention for Volkswagen at January's hearings for the 54.5 mpg CAFE standards because it builds efficient diesel cars that don't get the same benefits as hybrids despite similar fuel economy. It would also seem such numbers benefit niche automakers like Tesla, which earned a 346.8 mpg CAFE rating, or larger automakers that can dump funds down a sinkhole to appease a political process. The numbers can also be shuffled around to offset inefficient vehicles. For example, Mercedes-Benz is bringing its compact B-Class to the U.S. in a few years so it can keep producing 600-horsepower AMG super models that maybe get 15 mpg going downhill in a tail wind. Not all cars are created or tested equally, either, as the EPA tests just 10 percent of new vehicles at its Ann Arbor facilities, relying on automakers to be honest with their figures for the other 90 percent. The test routes used to calculate fuel economy are based on 1960s traffic patterns in Los Angeles. Needless to say, if anyone is achieving EPA numbers in today's much more congested L.A., we want to know how. None of this is particularly easy to follow for the average person, but if there's an observation to be made from all of this information, it's this: The number you see on the sticker may not be the one you get, and results may vary. Sources: Chicago Tribune