I thought that looked like a leak, the underside of the head shows it too between my hand and the plug. I was expecting a heavier deposit or more sludge than what's there. Okay, sounds like I have a plan for tomorrow then... pull the jug, inspect it, examine the piston and rings, clean the head surfaces and lap them, reassemble if everything's good... I have some (red) gasketmaker, is that a bad thing when reassembling one of these? I can pull a (factory) head gasket out but am without access to any other resources right now, except for stuff from the recycling bin.