Gas-Saving Moment of the Day: Measure in Gallons Per Mile

The standard measurement for a car's fuel efficiency is, as we're sure you're well aware, the number of miles traveled on a gallon of fuel. Now, researchers at Duke University have demonstrated some shortcomings of this measurement.

Through a series of experiments, they showed that fuel consumption is not reduced at an even rate as efficiency improves. This means that switching from a car that gets 18 mpg to one that gets 28 mpg will save you much more gas than moving from a 34 mpg vehicle to a 54 mpg one — 199 gallons versus 109 gallons, to be exact (you'll note that these numbers are slightly different from the New York Times blog post, but you can check our math yourself).

The team recommended that government, automakers and consumer publications (whoa, that's us!) supplement mpg with the metric of gallons per mile by listing vehicles in terms of how many gallons of fuel they use per 10,000 miles. Therefore, a 25 mpg car would become a 400 gallon per 10,000 mile vehicle. A 35 mpg car would use 286 gallons per 10,000 miles. They'll probably have to think of a way of saying that in less of a mouthful, but you can check out the efficiency chart here.

Although this is more of a long-term goal, the researchers make a great point, which is that even small increases in fuel efficiency can have a major money-saving impact. For instance, swapping a 12 mpg SUV for a 15 mpg ride will save you 167 gallons of gas over 10,000 miles. At $4 per gallon, that's almost $700.

The Illusion of Miles Per Gallon (Wheels)

Related:
More Gas-Saving Moments of the Day (KickingTires)

Comments

[Tony]

In Europe they been doing this as lond as I can remember myself. They measure efficiency in Liters per 100 km.

[Aaron]

This is certainly a much more helpful way of representing fuel consumption but I'm surprised it took "a series of experiments" by Duke researchers to do this simple math :).

[Jeffrey Davis]

This is an important point, and deserves a little more explanation. The important point is that the number of miles driven tends to be constant. Buying a Prius doesn't suddenly make you drive twice as far. And one doesn't buy a constant number of gallons, whether you're driving a H3 or a Fit. Gal/mile reflects our actual consumption, while miles/gal doesn't.

[Carlos]

I've been computing the cents per mile of our Toyota Matrix (16 cents/mile) vs. Toyota Sequoia (26 cents/mile), which makes you rethink the cost of something that was previously trivial like driving to Blockbuster to get a $3.99 movie.

[LM]

I've been telling my mom now that her 30 mile jaunts are costing $7 round trip and she thinks twice. This in a Scion xA. In my car, that would be $10. Yikes!

[ilija]

And they needed to do "study" to figure out this???? This is elementary school level math problem that can be solved in 10 minutes by a kid.