I have always used Mann oil and fuel filters on my Mercedes cars. The best oil is a name brand with an API rating of SN. API is the American Petroleum Institute. Avoid oil with an API rating of SA as this oil is made for vehicles built in the 1920’s and has no additives. Refer to your owner’s manual for the Mercedes recommended viscosity of the oil to be used (depends on climate where you live and other factors). By the way, a lot of people think the W in 10W30 oil stands for weight, when in fact it stands for winter, meaning the oil was formulated to be used during the winter.
I am in California and only use CASTROL GTX 20/50. This was recommended by METRIC MOTORS, INC. who rebuilt my engine.
Oil threads often take on a life of their own but I usually can't resist. I used Diesel-rated 15w40 in my 560SL for it's increased zinc content as recommended to me by someone who's knowledge I respect. AMSOIL was my choice.