The first thing I noticed after switching to Mobil 1 was occasional smoke from the exhaust on decel. I'm in the midwest so it's now super cold out and this car sits outside, not garaged.
Recently I drove it and noticed that it was smoking even more than before. I opened the fill cap with it idling and whoosh, lots of pressure so I ordered the PCV repair kit from FCP Groten. I pulled it in the garage last night to melt the snow and ice off so I can replace the PCV system (box and hoses). I knew the oil was low (not showing on the dipstick, consumption wasn't a problem before btw) so I added a qt and noticed that it's not draining well as it burped back out of the fill cap and I've never seen that happen with an older Volvo engine. The cams look clean too, not sludged. The engine has 188K miles.
I'm trying to speculate why the oil isn't properly draining as I doubt that that's due to the present clogged PCV system. Might the Mobil 1 be somehow clogging the cyl head oil drains in the head and why? I'd think that it'd flow better than petroleum oil? The engine's perhaps been driven 2K miles at the most since I switched to Mobil 1 last october.

Any ideas? Should I drain the Mobil 1, use petroleum oil again and hope that it'll become normal again?