>Posit two Beetles. Both are identical mechanically, they have identical
>bodies and they are driving down identical, perfectly flat roads. One
>Beetle weighs a hundred pounds and the other weighs a thousand pounds.
>
>Disregarding the friction in all internal mechanical
>components--considering inertia only--once they reach a certain steady
>speed, will they get identical gas mileage?

Yes.

-Tom