- leaving it in gear is a habit for me...

 

Go ahead. If I get mad, it'll only be for a little while.
Besides, the stuff I've posted is my opinion only and not written in stone. I don't have a problem with a difference of opinion. However, if you state something that goes against the laws of physics, you're fair game.

 

I always leave my car in gear and use the parking brake. If you park on a steep hill, the parking brake may not hold the car in place unless you pull up on the parking brake really hard. The same is true if you were to rely on the compression of the engine by putting the transmission in gear on a steep hill. The engine may hold the car at first, but it could slowly roll as the engine turns ever so slightly.

It is best to use both the Parking brake (thats why it is called a parking brake) and the compression of the engine both together. The engine complements the parking brake and the parking brake complements the engine. Why take a chance? By using both, the odds of a run away car will be dramatically reduced verses using just one ore the other.

If I drive hard in the mountains, I usually let everything cool off for about 4-5 miles before using the parking brake, or I will park on a perfectly FLAT surface and just use the engine. After a lapping session on a closed course, I do one cool down lap at slow speeds to allow cooling of the brakes, then pull into the paddock area which is FLAT and just use the engine to hold the car. All other scenario's, I use both the engine and the parking brake.