bkdc

What’s the weight of choice for my 2015 S550 rear differential fluid? I’ve always used GL-5 75w-90 in other cars but I’ve read Mercedes recommends 75w-85.

Plutoe

75W85

seamus2154

There is a specific spec for the W222. Check for your year. There were only a few manufactures meeting that spec other that MB. Fuchs Titan met the spec for the 2016. I think it was 235.7?? Mobil 1 tech line told me specifically they did NOT meet the spec for that rear and told me I should not deviate from the spec and recommended Fuchs Titan....I thought that was cool of them?

bkdc

The rear diff is MB 235.7, but I do not believe that for something like the rear differential, one must meet the manufacturer approval. I doubt there would be any issues running any GL-5 oil, whether 75W85 or 75W90, in the rear differential, and I'm pretty certain there aren't premature rear differential failures when any decent GL-5 oil is changed every two to three years. The bigger problem is when the rear diff oil isn't changed enough.

seamus2154

Well its your car, and your problem if your wrong. When a company like Mobil 1 knows of the spec and says we don't meet it, don't use it....I figure there must be a reason. I have seen many issues over the years with the wrong fluids being used in certain cars. Some have very specific needs because of design. I didn't care to experiment on my car, and didn't have the time to see if it was just branding or them paying for the spec? It was readily available, cheap enough, and I change my fluids routinely anyway...no need to skimp by.

konigstiger