Just was curious, for example your compression is 150 across. How much on general should it decrease every 10k miles?

 

Zero, is what it should do and what you hope it does. Only time it should go down if something harms the motor.

Over a very long period of time, the engine will wear out on its own causing compression to leak from various places out of the CC but not over 10k miles.

 

should regular maintanance be the deciding factor? what are main things that cause compression to weaken, is it rod knock?

 

excessive boost

 

Excessive boost, lack of oil, bad cams, etc. There are a lot of things that can cause it, but boost is the most common reason.

 

Thanks for responses guys. By excessive boost does that mean high boost, boosting all the time for no reason or comvination of both

 

Combination of both. Know your motor's limits, like how much boost your set up can safely run. If you hit boost 24/7, your engine will wear out significantly faster than if you drive with a lighter foot.