1992 300E Oil Viscosity/Consumption

[92 300E]

Hello! I'm new to the forum, and I just acquired my first Mercedes; a 1992 300E with 93,000 miles on the clock. My questions are: What is the recommended oil viscosity for this engine? The previous owner has been using Mobil 1 synthetic 10w-30 weight. I have noted some oil consumption, perhaps a quart every 1,000 miles. The cylinder head was reworked with new valve stem seals at mileage 79,000. Also, on cold start-up there is some chain or valve train (?) rattle for a few seconds; should this be addressed? It does not occur on every cold start.

Otherwise, the car runs and drives very well.

Thanks for any advice.

Nick