FCP Euro sells
ONLY THESE TWO fluids for a 2004 SLK320 diff, so I'm pretty comfortable using them.
https://www.fcpeuro.com/Mercedes~Ben...b=10&d=1007&v=Liqui Moly LM22090 - 75W90 Fully Synthetic Hypoid Gear Oil
Red Line 57904 - 75W90 GL-5 Gear Oil
And all of the other gear oils I've listed above are no different in specification to the Red Line fluid sold by
FCP Euro (I.E., all synthetic 75W90 GL-5 hypoid gear oil containing LSD friction modifiers).