While it’s not a M-B I’m sure many in this forum have opinions on motor oil. It’s an early 80’s Cadillac with the 4.1L engine that has a bottom end knock at idle when warm. I can’t hear it when cold or if I rev the engine so I assume its excessive clearance in the bearings somewhere. Since it doesn’t knock when cold at which time the oil is thick, why not have the oil thick like that all the time (discounting the cold start problems for now) by using 50 or 60 weight or even 70 weight oil? This is a cheap beater so actually fixing the problem is not an option.