Not an easy one to answer
I used to always leave in gear (an point wheels to steer into kerb) especially with disc handbrake mechanisms as when the disc cools it shrinks and if handbrake not applied firmly may loose enough friction to cause the car to run away (drum brakes are the opposite and actually increase the handbrake forse as they cool)
However it's not as simple now:-
1)You shouldn't leave a DMF permanantely in tension - after applying hand brake in gear as you release the footbrake the car will roll slightly potentially putting DMF springs/cogs into tension (The DMF usually has a number of different strength springs to ensure smooth takeup)
2) If you have an oil pressurised cam chain tensioner you should always leave in the gear on a hill that would turn the engine in the normal direction of opertaion - if you force backwards especially where cam shafts drive other gubbins (high pressure fuel pumps etc) the tensioner side of the chain carries the force required to turn the camshafts which can push the tensioner (especially if worn) back leaving the chain slack ready for the next engine start-up. Some manufacturers eg Chrysler - stipulate not to turn engines backwards in their service manuals
I myself do leave in gear but in 1st for pointing down a hill or reverse for pointing up a hill. However once I've stopped I now don't release my clucth until I've turned the engine off, put in gear , applied the handbrake firmly and released the footbrake
Edited by Big John on 19/03/2016 at 19:53
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