MPG calculations

[fuziduck]

Ok, if I'm wrong then fair enough but I'm not gonna get it so might as well just give up there.

OK one last ditch attempt at explaining it.

Lets say you have one gallon of fuel. You accelerate and use all of that fuel in one go in which you cover 20 miles. Now by the time your fuel is used up you are doing 100mph, and your momentum allows you to cover another 20miles with no fuel.

From start to finish you have covered 40 miles therefore for that one gallon of fuel it makes 40mpg. Not 20mpg as you would say. You must consider the momentum the car gains.

If you were to brake as soon as you ran out of fuel, the momentum would be turned into heat and then for that gallon of fuel you would only get 20mpg, hence why it is beneficial to not use brakes when aiming for high mpg.