Which fluid to use?

[orignalS60]

I'm running a v8 quattro rear end in my urs6.
Some places say to use 75w90 and other including
all-data say to use SAE 90 hypoid gear oil.
Which one is correct?

[RichLV]

I'm running a standard rear diff in my UrS4, Autodata tells me to use 75w90 synthetic. Which I did and it's running well.

[orignalS60]

I know the stock urs4/ urs6 rear differential uses
synthetic 75w90 but I wanted to be sure about the
v8 rear diff.

[Pauliusb2]

Acording to my system its GEAR OIL EP80W90 GL5 and it holds 1.7L.