Gentlemen:
525i M50 manual (1991) US spec. built in Dec 90. 138Kmiles
About three years ago I burned out several exhaust valve and got a "value job". All the exhaust valves were replaced and re-ground the intakes. New chain for the cams only with a new tensioner. Also had a blemish on the cam that was polished out! I did have a noisey lifter, especially in the winter, but couldn't identify it. Most everything else was put back in, stock.

Recently, at low rpm's under load, I get a clatter or pinging, I don't know which. It goes away and is intermitent, depending on driving conditions.
I'm running Mobil 1 (15W50) in the summer, and just recently put in a pint of Bardhal 1 Oil Conditioner, and the ping/clatter appears less prevalent.

I don't know if any of this is related, but is this something you experts may be able to comment on, please

Best regards,
Helm