If you are buying at Wal-Mart or your name brand auto retailers, you should be using 0W-40 for your 96 E300. It's the European car formula that meets the MB diesel standards. The one the dealerships uses (at least by me) is Mobil 1 5W-40 European Car Formula. But the 5W's at the retailers is either a different blend than what the dealerships get or the labeling is specially made for the dealerships. Because what the dealerships sells is not sold in in the stores. (at least the labeling is different, because the 5W in the stores does not specify "European car Formula"). Personally I think either blend is fine, but if yoy want to get what meets the standards of our cars, get the 0W-40. (I know... the never ending debate. Many threads on this).

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Mike Mass
Freehold, NJ

1999 E300 TD 178,000 miles
2007 E320 Bluetec - Sold

1998 E300 TD - R.I.P.