I have a 2004 WRX wagon (more or less stock) with 108k miles (which I love and is otherwise fairly good shape given it's age). When I was driving last week, I hit 5k RPM and suddenly the engine started making a clanking/knocking noise. I promptly brought it to a mechanic. To my untrained ear...

2003 with blown head gasket dont know were to start.

I just purchased a WRX and decided to take it to Quick Lube for the first oil change (first time I haven't done it by myself on any car). I got the correct Mobile-1 Filter and asked them what kind of oil they'd be using. They put in 0w-30 Mobile-1. My engine was hot and they drained it after it...