Engine ticking when warm
Just got hold of a 95 520i to replace my 92 525i which had badly rusted fuel lines. The 95 needs some suspension work, but is overall in better shape than the 92. Both cars have the M50 engine. The 95 does do something sort of disturbing, though. After it's been running for a bit, the engine starts ticking. I assume it's lifter noise as it speeds up and slows down with engine revs. It takes longer to start doing this when it's cooler, and happens rather quickly on warmer days.
I've done some reading about engine sludge, and wonder if that is the problem. I just changed oil using a high mileage Castrol anti-sludge oil in 20W/50. The underside of the oil cap was clean, and I didn't notice any black gunk in the engine itself before I started adding the new oil last weekend. The car doesn't seem to lack power from cold to warm. The engine doesn't chatter at all during a cold start up, only after it's warmed up.
Any thoughts from the experts?