It never made any sense to me why he kept the gasoline engine for propulsion, when he had a Mr. Fusion attached to generate however many gigawatts of electricity to run the time machine. Why not replace the motor with an electric, and bleed off a few kilowatts to power it? Of course, then you wouldn’t have the hooks for the story about needing gas and stuff.
But he didn't keep the gasoline engine.
Do you not remember the end of the first movie, when he did have the Mr. Fusion (instead of using Plutonium from the Libyans, or electricity from the clock tower lightning strike,) and was stuffing banana peels and beer cans into it, he ended up flying off, not driving off.
