Sunday’s NY Times article “The Last of the Power Rangers” predicts the eventual disappearance of the 500+ horsepower luxury sedan. Now that Obama has unveiled new fuel economy standards of 35.5 MPG by 2016, the extinction seems inevitable.

It got me thinking again about the way we consider fuel economy in MPG vs. GPM. The article states that the thirstiest performance sedan is the 2009 Cadilac CTS-V, coming in at 11 MPG. If you look the cars gallons-per-mile, you see it burns 909 gallons of fuel for 10,000 miles of driving. With this perspective, you can see how truly bad low fuel economy vehicles are, and how the MPG standard hides the truth about how much fuel these cars burn.
Assuming average mileage of 10,000 a year, we divide the MPG into 10,000:

Car 1: 11MPG= 909 gallons per year
Car 2: 22MPG= 454 gallons per year
Car 3: 33MPG= 303 gallons per year

Using the MPG standard it looks like the difference in economy between Car 1 and Car 2 would be the same as between Car 2 and Car 3. However, using GPM, we see that Car 1 uses twice the amount of fuel as Car 2, while Car 2 only uses one-and-a-half times the fuel of Car 3. The improvement in fuel economy at the lower end of the scale has a significantly different impact than from the higher end. That equates to thousands of gallons over the life of the car.

Duke researchers Richard Larrick and Jack Soll have much more information on their blog, and in the video below: