In your owners manual there is an extensive list of recommended oils. I'll fax mine to you if you don't have it. I have a 91 560 SEL 97K miles. It "uses" more w/ Mobil 1 0w-30 than Penzoil 5w-30( lazy in the winter, Jiffylubed ).
There's a big oil thread going on ...again. I change Mobil 1
every eight weeks, not that I need to, Just because I can.
Hope your's stay's tight!!