Found the Cause of the Oil Leak

So yes, BMW Boxer engines are known to 'use' a bit of oil during regular operation. I frequently check the oil level and had been regularly topping things off as needed and not giving it much thought.

However, that changed when I started noticing some oily stains on the bottom area of the left side cylinder cover and around the oil filler cap.

I could not spot any obvious leaks both with the engine hot or cold. I was also having to top off the oil level a lot more often than normal so I was a bit concerned.

I went to beemer dealer to get a new O-ring for the oil filler cap thinking perhaps that was the cause of the leakage. The parts guy asked me at the time if I wanted to replace the plastic insert as well. I'd not even thought that piece was replaceable so had not closely looked at it. Since it was only a few bucks I went ahead and got one as well.

I discovered when I removed the old insert (it just pops out with the aid of a flat tip screwdriver) that somehow dirt and sand particles had collected around where it seats into the cylinder cover and its own O-ring! I believe this is what was causing the oil seepage of late.

So I suppose I could have just simply wiped it clean and put it back in place but went ahead and put the new insert and O-ring in place. I cleaned off any oil remnants and its been over 700 miles since I did this and the oil level in the oil sight glass has remained rock steady; no evidence of any oil seepage either.

I am pleased with this easy fix and post it here for other Boxer engine riding owners to perhaps benefit from this experience of mine. See below picture, it's part #5 and 6 that were replaced.