Maybe I missed it but has the pan ever been off? When I got my slant I don't think the pan had ever been off because its a pain to do. Anyway there was about 2 inches of gray sludge in the bottom of the pan. I'm sure it was always low on oil because the oil was being displaced by the sludge. So even though it read okay on the dipstick but there wasn't enough in the engine.
Also when my 318 spun a rod bearing it was knocking not squealing. Good luck!
