Quote Originally Posted by Eric the Half a Bee View Post
If a car had one gear you might have a point, but it doesn't, so it's nonsense.

For example - suppose I drive for 5 miles at a constant 30mph. One day I drive the whole 5 miles in 4th gear, the next I drive it in 1st. According to your comment, I'd use the same amount of fuel both times.

Cars use gears. The energy used by the engine results in revs per second. 2000 revs per second uses the same amount of fuel regardless of gear.
pretty much all cars can manage to do 20mph in 3rd or 4th gear though, no need to drop to 2nd