I want to change the oil in the rear diff, I can see the drain plug and fill plug, so that's the easy part. I can't find the correct oil though. My hadbook says it is Castrol SAF AG4. Problem is I can't find any oil of that specification on the Castrol website.
Scudaria list the oil as:

Audi VW Gear Oil Synthetic 75W90 - Genuine VW Audi G052145S2

Is that the correct one?

 

Thanks, I'll order in a couple of bottles.