Not sure on what Hydraulic Fluid to use. Hyster parts told me J20C. I had to replace a couple hoses. I noticed that the fluid is blue in color. It's also used inside a freezer most of the time at -12F.

Hyster Forklift
Model N35ZDR3-16.25

J20C is clear or Amber in color from what I can find. Not sure what type of oil it is or if I can mix oil? It did lose like a gallon of fluid, maybe, maybe more. Hard to tell exactly.