Ditto to ya, Kev, that white milkshake goo under oil fill cap is from condensation mixing w/ oil vapors there, my Subie does that some in cold wet weather. Oil fill cap is prob. cooler than surrounding material and so water vapor condenses there. A decent AOS like the one I made will catch much of the water vapor. I'm letting mine fill w/ water/crankcase vapors all winter long so I can see how much it traps by springtime. For the Subie, I found that I had to do a modified PCV re-route in winter-I left the PCV connected stock, but installed a restricter in the hose. If I re-route it fully, w/ man. vac. capped, this engine gets too much water condensation in crankcase. The Subie engine is all-aluminum, it heats/cools rapidly, and in winter, it's like a water collector! Of course, now that I have this all sussed-out, we are having a dry warm winter here...As you guys up North and East are gettin' slammed...
When thinking about PCV re-routing, idle air control valve mods, and other things, If I'm concerned w/ someone in another area, I consider what the climate there is like...
Tracy G