Jul

2

The math of fuel economy

Filed Under Sunrise on KGMB9 

Don’t fret if you don’t get this right away. I didn’t, either.

Miles per gallon is a ratio while gallons per mile is the actual burn rate of the fuel in your car.

A 10 mpg savings can be greater than a 20 mpg savings — if the first is a 18 mpg (big SUV) to 28 mpg (station wagon) and the second is an improvement from 34 mpg (small car) to 54 mpg (hybrid).

The reason is that a mpg improvement of X is actually a greater amount of fuel saved when the improvement occurs at a higher burn rate.

See:

  • 100 miles/54 mpg=1.85 gallons burned.
  • 100 miles/34 mpg=2.94 gallons burned.
  • 100 miles/28 mpg=3.57 gallons burned.
  • 100 miles/18 mpg=5.56 gallons burned.

This means, of yours is a typical household with two vehicles, one of them an SUV and the other a regular car, you can reduce your fuel bills more by trading the SUV for a vehicle that gets 10 mpg better mileage than by trading your car for a hybrid for a 20 mph improvement.

 

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