Mike,
I have 3 different types of hydro fluid running through my system. I bought multi G 134 at one NH dealer and then bought 134's replacement (Ambra Mastertran Ultraction) at another NH dealer. I was assured by staff that the new stuff is compatible with the old version. I did look up my tractors requirements for this hydro oil and the manual states 10w30. Later while using a land leveler I discovered that one of my hydro connections had a leak and I think lost over 3 gallons in the red dirt. In a rush I went to Attwoods and found "Star Fire Premium Tractor Hydraulic oil" that was also 10w30 and 5 gallons for $27. That less than $6/gal and I was back in action. It not ideal but the tractor doesn't appear to care and I was back on the stick. As long as you meet the requirements I think your going to to be ok.
