The idea is in principle fine. Using any power source you can make something resembling a car. From ethanol to gasoline to rocket fuel to a bunch of cats on a hamster wheel and the food you give them.

A plutonium car would be a bit much. For one, cars aren't using a very small load of power continuously, they use a lot of power intermittently.

Two, plutonium is expensive, we get most of it by literally making it from other elements essentially atom by atom. This makes it a bit more expensive per joule than gasoline.

Three, plutonium is decently dangerous.

Etc etc.

Technically possible, not a practical alternative.