[gjm120]

A while back I did a differential fluid change using BMW branded SAF-XO 75W90. Now thinking I might have used the wrong fluid.

In RealOem a different part number is shown for differential oil from 07/2011 onward. I know part numbers can change with no change in the part itself, but, it seems the pre 07/2011 oil is a 75W90 GL-5 spec while the 07/2011 forward is 75W85 GL-4. The viscosity isn't my concern, it's GL-4 vs GL-5, specifically the additive package and the way it attaches itself to surfaces.

(initially dug into this when looking into gearbox oil for my old British motorcycles)

Anybody know anything about this? Those with newer cars, what differential fluid did you use?

I'm not hugely concerned since I don't put on a lot of miles and some gear oils carry both GL-4 and GL-5, but, since BMW decided to change spec in 2011, might be worth investigating.