Originally Posted by NitroGod777

I've heard from a couple of people that if the mystery oil is used without an engine cleaning then it's more likely to get gummed up over time. If it's gonna be stored away for years then it a better idea to strip down the engine and then apply after run oil/ATF/other types.

Personally I had got one used engine from eBay for $13 that was pretty tight and very difficult to turn. The seller did tell me that when he had put it away it still had good compression. When I took it apart the crack, piston, connecting rod etc had some greenish jelly like substance and the grease from the ball bearings had hardened into small pieces that it was moving around the crank and jamming it. Had to soak it first in WD-40 for a good couple of minutes and then only I could get it to start turning and then continued with the stripping and clean process.