I've been looking to replace the differential fluid in my car...
Castrol SAF XJ 75W140 that is.
Called two BMW dealers in town, last year it was only available in 55 gallon barrels, this year it is available in 0.5L quantities, but here's what I was quoted:
Dealer A: $80/bottle
Dealer B: $50/bottle (parts guy said this is still cheaper than bringing the car in)
Luckily I googled "Castrol SAF XJ", and apparently the C63 uses the same fluid.
So I called the Mercedes dealer in town and was quoted:
$17/bottle
End of public service announcement.
P.S.: Thanks AMG