For my 1991 and 1992 300D's, I'm committed to using a Mobil synthetic 5w40, either Turbo Diesel Truck or Delvac 1 (most likely the former, since it's less expensive). From anything I've ever seen on this board, if the assumption is I'm using a Mobil synthetic, that's the way to go.

However, I found it curious that, on the Mobil site, their recommendation for my cars is Mobil 1 0w40 with SuperSyn. They don't even give the 5w40 as an option.

I assume Mobil engineers (and marketers?) know whereof they speak. But I also have the highest regard for the consensus of those who post here.

Can anyone help me resolve the discrepancy?

Related question: Why, in Mobil's opinion, would 0w40 be a better choice?

Thanks.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

http://www.mobil.com/USA-English/MotorOil/Car_Care/AskMobil/Using_5W-40_Motor_Oil_in_Mercedes-Benz.aspx

"as it is specifically designed for your type of vehicle" (Abovementioned Mobil web page).

Sounds like a fairly generic recommendation, not specific to your car.

Personally, I prefer a narrower range. Viscosity modifiers (what is added to create a wide-range multi-viscosity synthetic or any multi-viscosity dino oil) are by nature fragile polymers, and do not shear well. Further, the oil base-stock used for a multi-viscosity oil is thinner with a lower xxW number, so it likely will shear/protect like a thinner oil in high-shear points (turbo, cam lobes, etc.). Conversely, Mobil 1's original (now extended-drain?) 5W-30 had NO viscosity modifiers, making it a very stable oil.

Provided the oil meets the spec, I'd use the thickest oil that is in your temperature range per the car's operator's manual. Further, if your OM602 is tuned stock (no visible smoke), you are fine with any oil rated CD-x, it will handle the minor soot loading and the base-number will be fine with ULSD.

I'm happy with TD&T. Used to run Delvac 1, but too hard to find and too $$ for me to justify since the TD&T became available and is a group IV also.

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Gone to the dark side

- Jeff

Mobil 1 0W40 meets ACEA B2 B3 and B4 specifications which is the rating we MB diesel owners should follow, not the API rating system.

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1993 W124 300D 2.5L Turbo, OM602.962
2000 Chevrolet Cavalier, 2.4L DOHC
2002 Ford Explorer, 4.0L SOHC
2005 Toyota Prius, 1.5L

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