Fuel-Economy Fallacies

One burning question for all vehicles, not just hybrids, is whether they really achieve the Environmental Protection Agency's fuel-economy estimates posted on a new vehicle's window sticker. The answer is…sometimes.

Experience over many years has shown that conservative driving can lead to the city and highway fuel-economy numbers the Environmental Protection Agency tells us we should be able to achieve with a given model. But then, who among us really drives that conservatively?

How and where you drive greatly affects fuel economy. The mileage estimates on window stickers aren't always an accurate reflection of what to expect in real-world driving.

This is an especially hot topic with hybrid drivers. In fact, it's been widely reported that real-world hybrid fuel economy is lower than official EPA estimates by a substantially wider margin than conventional vehicles. This is no doubt due to the idiosyncrasies of gasoline/electric propulsion and the EPA's laboratory test procedures, which were designed long ago and are in need of updating. In fact, there's substantial pressure on the EPA to revise its testing procedures to reflect real-world driving and generate more accurate fuel-economy figures, not only for hybrids but for all vehicles. Read more about this in The EPA's Ancient System.

The Union of Concerned Scientists reports the disparity between estimated and actual fuel economy for vehicles in general as high as 30 percent. Additionally, a Consumer Reports study that examined the fuel economy of over 300 model year 2000 to 2006 cars showed highway mileage reasonably close to EPA estimates, but a disparity of 35 percent to 50 percent in city driving figures. Interestingly, while hybrids in the Consumer Reports testing averaged 19 mpg less than EPA city fuel economy estimates, three hybrids still ranked among the study’s top five spots for fuel economy.

This underscores a simple point: While it may be that hybrid vehicles often fail to achieve the ethereal estimated fuel-economy figures on their window stickers, they are still generally achieving the highest fuel economy of any vehicle on the road and are worthy of your consideration.