LOL. How does that even work? It takes the same amount of work to travel at the same distance.
Not quite. The difference is small, but it's there.
There are two main coefficients of drag imposed on a moving car. Both act as forces being applied to the mass of the car to cause deceleration (actually an acceleration).
These are road drag (the friction of the tires as they rotate, flex, contact and release the road pavement, axle friction, etc.; and aerodynamic drag (the car is also moving through the air).
Best mileage is when these two are essentially balanced.
At slow speeds, road drag is prevalent. As the car speeds up, road drag actually begins to reduce, since tire flex and road friction is reduced (even the effects of axle drag is decreased, due to the characteristics of grease at high speeds). It also means aerodynamic drag increases.
At higher speeds, aerodynamic drag is prevalent. At such speeds, you can actually feel the car 'flying' instead of just rolling along.
At 55mph, the transition begins. You can feel it as the uneven behavior of the car (depending on local breezes and road surface variations). Mileage is worse.
At too slow a speed, mileage is worse.
At higher speeds, mileage actually improves, as the car transitions more to aerodynamic drag. The best mileage is when you feel the vehicle smoothly 'flying' at the minimum speed to do so. Typically, this is around 60mph to 65mph for most cars.
Forcing lower speeds to 'save fuel' is itself fascism. Who is the government to tell me if I want to save fuel or not? If I want to drive faster and use more fuel to do it, that's MY choice, NOT the government's!. Remember, it is MY fuel that I buy. I own it. I can do what I want with it.
The ONLY thing about any speed limit is safety, and only related to the road itself, NOT due to some political or economy managing from the government!
It the road is built to handle 80mph, I should be able to drive 80mph.