More MPG math:
June 22, 2008
The New York Times’ always-great “Wheels” blog points out that “miles per gallon” perhaps isn’t the best metric, or at least shouldn’t be the only metric, of fuel savings. A higher MPG figure gives the false impression that the savings are proportional to the mileage. Obviously, a higher MPG rating is always better, but as the fuel efficiency increases, the savings start to level off. Their example is that replacing a low-mileage SUV with an average-mileage car makes a much bigger fuel cost difference than trading an average-mileage car for a hybrid car. Let’s do some math and see what that means for scooters.
Of course, this ignores vehicle price, maintenance, taxes, insurance, etc, we’re talking strictly fuel savings. We’re assuming a gas price of $4 per gallon for our example:
- An 18mpg SUV uses .0556 gallons per mile (22.2¢ per mile)
- A 28mpg car uses .0357 gallons per mile (13.9¢ per mile)
- A 54mpg car uses .0185 gallons per mile (7.4¢ per mile)
- A 60mpg scooter uses .0167 gallons per mile (6.7¢ per mile)
- A 100 mpg scooter uses .0100 gallons per mile (4¢ per mile)
So if you switch from an 18mpg SUV to a 100mpg scooter (if such a thing exists), you’re saving almost 19¢ a mile. Boo-ya. No-brainer. But switching from a 28mpg car to a 60mpg scooter (a 32mpg difference, saving 7.2¢ a mile), actually saves less per mile than switching from an 18mpg SUV to a 28mpg car (a mere 10mpg difference saving 8.3¢ per mile).
A 100-mpg scooter sounds great, right? Sure, but it’s only saving about 4¢ a mile more than a 54mpg hybrid, not much considering the 46-mpg difference. A hypothetical 200-mpg scooter, awesome as it sounds, would only save an additional 1.67¢.
Obviously, you’re always saving more gas (and more money) with a higher-mpg vehicle, which is good. But your savings decrease as your mileage increases. In the same vein as sunscreen SPF and digital camera megapixels, a higher number is technically better, but after a certain point, the returns diminsh considerably. Just something to consider as you’re measuring your fuel savings or considering a scooter purchase.