Hi,
I was reading posts about changing the differential oil and came across your posts. I have a 300D 81 and looking to get that differential oil changed but having trouble locating SAE 90. I come up with 85w90 and all sorts of brands and wonder if Mobil 1 which is synthetic is really okay to use in older cars.....? Or should I get 90 as some people have told me but where do I find that? I've called PepBoys, OReilly....short of checking the parts dept at a Mercedes dealer. I'm located in Los Angeles. thanks