IN a car I've only done it once, that was about four years ago at an ex's parents' cottage because her family was all there and we couldn't even chance doing it at night. Her car was parked up on a ridge but we were still only 100 feet away from her whole family.
ON a car I did it about five years ago with my nympho whore ex - we were going to do it in the car and it was uncomfortable so I pulled onto a side concession, found an empty field and banged her on the hood.