I have a Case 580K and was using Hytran/Mastertran/ultraction or whatever name that was popular at the time. The manual says Case TCH Fluid but when I bought it from the dealer he said use Hytran. It was running me about $110 a 5 gallon bucket. I was using the cheap stuff at Tractor Supply Travellers Premium. I just started using Mobile/Delvac Tractor Hydraulic Fluid. It was either that or try Hygard by John Deere. I will say the HyTran stuff does seem to contain moisture very well. I've been rebuilding cylinders as they fail or replacing hoses. Every time it seems I lose maybe up to a gallon of fluid. I thought they pwere phasing out Hytran as my local ag dealer doesn't seem to carry it but I see I can get it on the CNH page for maybe $88 for 5 Gal.
Side note: Some time back I suggested to Project Farm to do testing on some of the popular tractor hydraulic oils.Maybe more prodding from members would get him to do it. He often sends the oils out before doing his own home brew testing.