See by reading by post, you learned a couple tidbits about your M54 engine (same as in my wife's 330i) as well? They are famous for leaking oil at the oil filter housing base. Just a small simple gasket. But the leak gets worse and worse from a couple drops on the garage floor to a big puddle. If you ever do that job, that is when you would want to change out the entire CCV system if old. Much better access! Those plastic hoses from the years of heat get so brittle, they break in your hands! And if up North, install the protected "cold weather version" of the CCV. Has a foam boot over it to insulate it.

Sorry to digress to the M54. Thought it might be helpful to you!??