Let's suppose I leave my car in gear when parking on a hill (besides using handbrake and turning the wheels towards/away from the curb, depending on the direction I'm parking in). In case that matters, let's suppose the motor is gasoline (but I am also interested in answers for diesel-motors).
By the two possible "gear directions" (is there a better term for this?) I mean the following:
Gears in the same direction as gravity, i.e. if I park pointing downhill, then first gear, if uphill, then reverse.
Gears against gravity, i.e. if I park pointing downhill, then reverse; otherwise, if uphill, then first gear.
I did some research, to find which one you should do, but found there is no definitive answer. This is what I found:
- If the gears are "against gravity" (i.e. reverse downhill, first gear uphill), then if the car accidentally moves, then the motor can be damaged by moving "backwards". (If I understood correctly, the reason is that the drive belt only works in the forward direction, and thus valves will hit against pistons.)
- If the gears are "in the same direction as gravity" (reverse uphill, first gear downhill), then if the car accidentally moves, the motor can jump start alone, and the car will move forward autonomously from that point.
- Newer cars cannot jump start automatically in the above case (only older cars).
My questions are the following:
- Are these conclusions correct?
- Are there any other pros/cons for the two directions?
- How are newer cars immune to being automatically jump started, if they move in the same direction as the engaged gear?
- How can I check if my car is new enough to not be affected by this problem?
PS: I'm already aware of this other question, which has been closed as opinion based, but I think that mine (1) isn't a duplicate, and (2) is not opinion based, because I am asking more concrete questions.
PPS: I also know that there are arguments against leaving the car in gear at all, when parking (some of them also mentioned in the question above), but they are out of scope for this question.