I've already posted this on a few BMW forums, and they don't seem to know for sure. I've had this ticking/knocking noise since I bought the car a few months back at 80k miles. It now has 83k miles. I think the noise is coming from back of the crankcase. Thing is, I just changed my oil yesterday and discarded it, so if I want to send it in for an oil analysis, how long do I have to run the fresh oil I just put in? Here's a vid: http://www.youtube.com/watch?v=dmRwrWMjiWM And BTW, car runs, feels and pulls fine.