I had a bit of a problem at the dealership today, trying to get the correct differential fluid for an '05 ML500.
The fluid should meet the MB Sheet 235.7 specification, and be of an 75/80W-90 viscosity. But the fluid they sell as "OEM" (Fuchs Titan Super Gear MC 80W-90) did not. It meets both API GL-4 and GL-5 (which I found rather interesting, since these seem not to be interchangeable in some applications), and various other manufacturer specifications like Scania and MAN's own spec. At $14 per litre, I told them to keep it.
Does anybody know if Mobil happens to carry a differential fluid meeting the MB Sheet 235.7 specification? My search hasn't lead me to find anything. Would it be alright to substitute something like Motorcraft Premium Rear Axle Lubricant 80W-90, and change it out at 40,000 km (25,000 miles) as opposed to the recommended 100,000 km (60,000 miles)? Thank you.
MB235.7 differential fluid
- Thread starter Falcon_LS
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I practice and dictate 30k mile changes for 'ends and xcases.
Don't get all scared by the 235.7 spec which is all but meaningless, as are many automaker specs.
I would use and recommend full synthetic gear oil always. Your location is a little bit warm and I would even consider using ANY 75w110 or 75w140 for better protection.
From what I understand, you require a GL5 gear oil that is either a full synthetic 75w85(fuel saving), or a thick 85w90(film thickness protects).
I personally replace all fluids and lubricants (other than motor oil which is changed sooner) at the 25k mile mark. But thick gear oil isn't always the best way forward, or rather depends on the application. I used SAE 145 in my truck and it made it feel pretty heavy, until I switched over to 80W-90. SAE 90 is as thick as I would go in mine.
That said, the requirement for this application is essentially a GL-5 oil, that's of an 80W-90 viscosity. 
No meed to elaborate o undummy's great post, except 'dittos'..
I agree. They are such a bunch of idiots that they really need such an expert to get on a plane to Stuttgart and sort them out. They clearly know nothing about formulations, oil testing, and test development in support of their approval process. The next time that I talk to them I will be sure to mention that expert advice is available should they see the need!
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