If still under warranty, just get the MB gear oil from Randy at EPS Parts (http://www.epsparts.com) or the partsforum here.

I personally run SWEPCO 201 gear oil 80w-90 from Pelican Parts. RC Imports who races MB swears by it, the Porsche Club, and so do I.

Get it here:
http://www.pelicanparts.com/catalog/shopcart/CARE/POR_CARE_SWEPCO-detail.htm

:-) neil