There's a long extensive list of MB recommended oils for the 3.2 engine. Use any one of them you like. I've always used Mobil 1 0-40 and it's one of Mobil 1's better multi-viscosity oils if bill the oil guy is real. Because of my climate and car abusage I may switch to Mobil 1 5-50, if I can find it. Also on the recommended list BTW.

MB 229.3 - Multigrade engine oils (Specification 229.3) - Mercedes-Benz Specifications for Operating Fluids

Les