A New View of Fuel Efficiency
By Charles Krome
In addition to my writing here at Autosavant, yours truly also has a number of other auto-related gigs, including a semi-regular spot on a weekly web-based “talk show” called Open Line (check it out on Mondays at http://bit.ly/OpenLine). And in this past episode, we chatted briefly about a new approach to fuel efficiency that I’m eager to try out on my fellow Savants.
Here’s my thinking: It’s always struck me as odd when vehicles in two different segments somehow ended up with very similar EPA numbers. For example, both the Ford Fiesta and the new Ford Focus are going to post marks of 40 mpg highway. Now, one way of looking at this is “wow, Ford was able to build a compact car that gets the same great fuel economy as its subcompact.” But I can’t help approaching this from the other side, wondering how, if the Blue Oval can get that kind of performance from the Focus, it can’t do better with the smaller, lighter Fiesta.
Clearly, the Focus is a more efficient package, since it’s delivering the same fuel economy even though it’s bigger and heavier than the Fiesta, right? And, by that kind of standard, a porky full-size sedan with even lower EPA numbers might actually be more efficient than either.
Thus was born what I humbly call the Krome Score.
What you do is calculate how much gas it takes to move a given car a mile, than divide that number by the car’s curb weight. What you’re left with is a measure of how much fuel it takes to move one pound of that vehicle one mile. (Of course, you have to do some adjusting of decimal points to make the numbers “look good.”)
For the Fords, the Fiesta SFE with the automaker’s PowerShift automatic weighs in at 2,575 lbs. as a hatchback and gets the aforementioned 40 mpg highway. Preliminary specs on the five-door Focus with the same transmission and EPA number show a 2,927-lb. curb weight. The outcome here is a Krome Score of .971 for the Fiesta and .854 for the Focus, with the lower number, reflecting the lower amount of gas needed to move one pound of vehicle, being better. Now, when you run the Fusion through this math, it gets even more interesting, because the number for Ford’s mid-sizer comes to .907, which means it too is more efficient than the Fiesta.
The two-ton 2011 Ford Edge? Again, more efficient than a Fiesta, thanks to the Blue Oval’s ability to wring 27 mpg highway out of a vehicle that tips the scales at 4,082 lbs.—the crossover also notched a .907 Krome Score.
Who’d have thunk it?