EPA Is Changing How It Calculates Fuel Economy Numbers

There is a lot of pressure on regulators and car companies to make their fuel economy numbers more realistic. Our European cousins complain the loudest and so they should. There is seldom any rational connection between the numbers they see at the dealership and what they can expect when they actually get behind the wheel and start driving in the real world.


Fuel economy

In an effort to make the numbers customers see on the window sticker closer to reality, the EPA has decided to change how it calculates them. As a result, about 30% of the cars in the American market will see a decline in their stated mileage by a mile per gallon or two. Most cars have not had their ratings changed and a few have actually seen their EPA mileage numbers increase slightly as a result of the change. The problem for shoppers is that a 2017 model may have a lower fuel economy number than a 2016 version of the same car, even though they are mechanically identical.

Byron Bunker, director of the compliance division at the EPA’s Office of Transportation and Air Quality, says the agency ran 1,209 fuel economy results from the 2016 model year through the agency’s updated calculations. 15% saw their ratings fall by 1 mpg in combined mileage. Thirteen, or about 1%, increased by 1 mpg. The combined mileage stayed the same for the remaining 84 percent. Cars.com did its own analysis of the 75 best selling cars in America and found nearly 30% of them suffered a decline in their EPA economy rating.

The EPA says the data it has collected since the last revision in 2006 better reflects today’s fuel efficiency technologies and it used that data to change the way it calculates the new ratings. The calculations have “a high degree of precision,” the agency says. Previously when making changes to the way it calculates fuel economy numbers, the EPA has gone back and applied the new method to all prior data so people could research and compare changes between different model years of the same car. The EPA has yet to do so for the latest changes, although it says it plans to do that and update its website accordingly “in a few weeks.”

Despite the fact that people are buying larger, heavier, and thirstier cars while gas prices are low, they still place a great deal of importance on the mileage numbers printed on all new car window stickers. A difference of a mile per gallon or two can sway people away from one model and toward another, which is why manufacturers scratch and claw for every advantage when it comes to their EPA numbers. While new window stickers are supposed to advise people that mileage ratings are being computed differently this year, Cars.com found that the notice was in very small print on some and missing entirely on others.

The biggest change seems to be to the rating for the Volkswagen Passat with the turbocharged 4 cylinder gasoline engine. Its highway rating dropped from 38 mpg to only 34 mpg. Its overall rating slipped two miles per gallon. The Toyota Camry Hybrid also lost 2 mpg from its overall fuel economy rating.

The changes made are small and anything that makes the numbers closer to real world experience is to be applauded. Sadly, the EPA has given the changes almost no publicity, which increases the likelihood that consumers will be confused by what the see on the window stickers for 2017 models. Greater transparency would have been a plus.

Source: Cars.com

Steve Hanley

Closely following the transition from internal combustion to electricity. Whether it's cars, trucks, ships, or airplanes, sustainability is the key. Please follow me on Google + and Twitter.