Posted a few weeks ago about changing the turbo oil cooler o-rings, because I was convinced, after seeing oil dripping off the end of the filter, that one of these must be the culprit. Well, I just went in and did an oil change, and it looks like the the areas of the oil cooler adapter with the o-rings that are prone to leaking are actually completely dry! I looked carefully at idle after the oil change for anything dripping off the filter, and it stayed dry. Then I did a 300-mile trip, checked again and once again the bottom rear of the filter is covered with (now fresh) oil.

So I'm trying to figure out where this oil is coming from. There appears to be a small rear main seal leak which has lightly coated the transmission case, but that sits well behind the affected area, and there's nothing coming from the area of the oil filter at all. The turbo lines are dry, and nothing is leaking from the top of the engine, like at the valve cover gasket, front seals, etc. Also ZERO oil on the driveway when the car sits, even for days. Is it possible that there is a small leak somewhere that opens when driving and oil is flung onto the back of the filter in this way? Has engine overpressure been known to compromise the oil filter seal in some way? I would think all the other seals on the car would blow before that one!

I'll be cleaning the PCV system shortly, and perhaps this might help things - but it would still be useful to know where this mystery leak is actually coming from!