If there's no obvious oil leak, it's probably piston blow by. Like you said, it's likely gunked up rings unless there are signs of oil and coolant mix.
Got my Neilson Powless Maryland race suit from @efprocycling.com. His run with the bike was one of the most memorable moments I've seen in 20+ years of viewing. It's going on the wall once I get a proper frame.
If you loved Alanis Morissette's hidden song, Uninvited, check this out. Pistols at Dawn featuring Mixi Demner of Stitched Up Heart. She's sort of smothered in this, but really nails an Alanis sound bumped up to 11.
