I saw this on Eric de Place’s blog and although not immediately intuitive, he’s right:
You save more fuel switching from a 15 to 18 mpg car than switching from a 50 to 100 mpg car.
|15 mpg||18 mpg||50 mpg||100 mpg|
|1333 gallons||1111 gallons||400 gallons||200 gallons|
So going from 15mpg to 18mpg, you’d save 220 gallons, but doubling your mileage from 50mpg to 100mpg would only save you 200 gallons a year, assuming you drove 20,000/year. So it really is important to pay attention to the car you pick’s gas mileage, even if it’s only a few miles more per gallon than another one.