Yes..this is similar to a comment I made in a different MPG post - there are big diminishing returns as you get higher. Someone who buys a new car and upgrades gas mileage from 16 mpg to 20 mpg will have a MUCH bigger boost to saving money that someone who upgrades from 26 mpg to 30 mpg. In Europe, the flip the equation to make it more constant. Its not kilometers to liter, but liter to kilometer.