Ironic, gallons per mile is actually a more useful measure for high fuel efficiency vehicles because it directly represents fuel consumption. Differences in MPG are more misleading to intuition as MPG increases.

For example, upgrading from an 18mpg car to a 28mpg car saves more fuel than upgrading from a 34mpg car to a 50mpg car. It is easy to be misled that 34mpg -> 50mpg is more savings because it is an upgrade of 16mpg rather than only 10mpg.