I have a 1998 ML 350 and always used Mobil 1 0-40. Now the dealer says that MB uses Mobil 1 5-40 for the E350's. I have a 2006 E350, should I use 0-40 or 5-40?

 

Please search. Your question has been asked and answered numerous times.

BTW

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The 5W-40 is the only one of the two suitable for diesels, and since dealership automatic oil dispensing systems can handle only one grade of oil, that's what they use. It's OK, but 0W-40 is what I'd use if I were doing it myself.

 

In addition, the 0-40 has more phosphorus. The 5-40 has reduced phosphorus to help protect modern emissions systems (ie, the cats) But phosphorus is the protective additive used by Mobil (their zinc equivalent.) And as Kent says, the 5-40 is formulated also for particulate filters of the diesel motors.

The OP can check the M1 website for more details. http://www.mobiloil.com/USA-English/...l_1_0W-40.aspx