Hi all, I just picked up a sweet 2004 WRX wagon:
It has 195,000 on it but runs strong and feels solid. I could tell before I bought it that it's been taken care of pretty well. Boost peaks at ~ 13 psi if my Cobb AP is to be trusted. The interior looks almost brand new and the body is in decent shape as well.
Only issue that I am sort of concerned about is the PO told me she burns about a half quart of oil between changes. I'm no Subie expert by any means, but just looking around the engine bay, I've noticed a decent amount of oil residue/grit build-up around the edges of the intercooler outlet hose. I have also read that Subies have a tendency put oil through the intake by way of the PCV. It's my understanding that the horizontally-opposed arrangement naturally lends itself to more oil mist being vented from the heads.
That all being said, I wonder if my disappearing oil could potentially be leaking, for lack of a better word, into the intake through the crankcase venting.
I think this may be the motivation behind air-oil separators and "catch-cans." I plan on testing this theory on my own WRX, with an inspection of the intake system both before and after an AOS installation. I plan on removing all of the intake piping (intercooler included) for examination and cleaning, then reinstalling with an AOS in place. I don't think I'll go 200,000 miles before the after-installation inspection, but a couple thousand miles should be enough to see a general trend.
I had a Ford Ranger before this that had a rear-main leak, it would drip on the driveway everyday, at work, etc, and it went through about a quart every 3k miles. Not really a problem if you keep on top of it, check the level frequently. I actually saw it as a good thing, because it kept me in the engine bay and crawling underneath. And everywhere there was leaked oil, there was no rust. Win!
What do you guys think? I've heard of brand-new WRXs with barely 500 miles on the odo having oil pooled inside the intercooler, so to me, this seems a likely occurrence. Aside from the decrease in intercooler cooling effect on the intake charge, and the small amount of burnt oil, is there any real downside to oil in the intake air?