Join Date: May 2008
Location: Spokane WA USA
Car: 2007 Outback XT Ltd
Feedback Score: 0 reviews
Leaking seals or gaskets, worn or broken oil control rings, scored cylinder walls, worn valve guide seals - they can all lead to oil in the cylinders. The pistons are VERY efficient at moving air, and when there is an opening into the lubrication system that isn't supposed to be there, they will suck oil in like you wouldn't believe.
It can be as simple as a stuck PCV valve that is letting oil into the intake, and from there into the chambers. That is the first thing I would check. If oil pours out of the pcv valve hose when you take it off, there is a problem. The valve contains a ball that acts as a one way check valve, if it doesn't rattle freely when you shake it, it is no good. They are dirt cheap, so you might as well just change it while you are there.
If you have eliminated external sources, then you need to go inside. To see where it is going, pull the plugs and see if any are caked with carbon. If so, there is your culprit.
Then you need to determine if the problem is in the heads or in the block. A pro can do some testing for you like a peek inside the cylinders with a boroscope and a leak down compression test. He will give you the bad news (head rebuild) or the REALLY bad news (new engine required).
Good luck. Hopefully it's just a PCV valve..... I would push Subaru hard on this issue.
BTW it is REALLY bad to not check the oil routinely. 4000 miles is way too long, as you discovered. 1000 would be fine. I check mine more often than that.
Spokane WA USA