I didn't know it was easier to make an extra demo account to login from other places to ask questions about the full game for which you need an s2 license.
Most of these things are too specific to be worth simulating.
You could just make it dependable on some variables, but I don't see how a 12 lap race should influence something like a differential.
However, what may be an acceptable solution, is to make it depend on temperature and time.
So if you were overreving the engine lots of times your oil temperature would rise too much, having certain effects eventually. (or at least make a significant top speed reduction)
Brakes could be done by braking time and input (max braking for a certain amount of time would ruin the brakes, although cooling it in the meantime would of course help.)
Cilinder failure or catastrophic failures do seem to random for me. We are all driving around in perfect cars, so why would there be inconsistencies?
If this would be a "build, repair and race"-game (à la SLRR), you could use this (wear and tear being the main factor).
BUT(!) in LFS we all start with the same car, in the same conditions.
How would you react if your opponent has 20BHP more than you because he has a randomly generated better engine and yours sucks?
That wouldn't work for LFS, or atleast until a multiplayer career mode is included. And we all know that is not going to happen.