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A car in an evacuated tunnel can move at high speeds with low fuel consumption, unopposed by aerodynamic drag. According to the simplified model presented in post one, the force to move the car will be the same at 10mph or at 30mph, and the fuel economy inside your vacuum environment will be the same at either speed. Power, i.e. the rate at which energy is converted from one form to another, will be linear with respect to speed. So your motor will be working three times as hard to go three times as fast. But nobody drives in an evacuated tunnel: it would be an unaffordably expensive toll road.
The moon is a different story. A car on the moon weighs 1/7th as much as it does on Earth, so you would expect to have 1/7th the RR for a given road surface / tire temperature combination, and virtually no aerodynamic drag. Good thing, too, because energy is expensive on the moon.
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