Mental Floss

Who Needs MPGs?

Ransom Riggs

Toyota's new slogan may be "I want my MPG," but some experts are arguing that MPG is a backwards way of measuring a vehicle's fuel efficiency. Instead, they say, we need GPM.

We Americans are no strangers to weird measurements. In metric-friendly countries, water freezes at 0 and boils at 100. In America, there are twelve inches in a foot and 5280 feet in a mile; breakdowns that are a little tough to wrap your head around compared to the powers-of-ten-tastic metric system. Our MPGs are an equally confusing measure. Treehugger recently blogged that the relationship between the amount of gas consumed by a vehicle and its MPG rating isn't linear ... it's curvilinear. I suck at math, but a quick look at this graph made the distinction fairly clear:

In other words, the gasoline savings of replacing a 15 MPG car with a 20 MPG car is about equal to the savings of switching from a 30 MPG car to a 60 MPG car.

Here's a quick breakdown of what gallons-per-mile looks like:

15 mpg = 660 gallons per 10,000 miles
20 mpg = 500 gallons per 10,000 miles
30 mpg = 330 gallons per 10,000 miles
45 mpg = 220 gallons per 10,000 miles
60 mpg = 160 gallons per 10,000 miles

ChevyTahoeHybrid2008GreenCa.jpg /