Hopinso I don't know when you were born in this lifetime but if it was after the apparent age of the car in the memory - late forty's early fifties then there is no reason why this could not be a valid memory.
Every experience we have ever had is there, its just that most of it is blocked out.
Particularly anything before this life, since there is some kind of a memory block put in place when we start a new life.
Without the memory block we would remember everything.
Some times people are able to get flickers of memory before this life and it sounds like your ride that nite down slaughter mountain may have opened a crack to a past life memory.