In Reply to: Re: Hydraulic Fluid Source posted by Jim on March 02, 2019 at 06:57:19:
No real consnesus - like engine oil there are some rather firmly entrenched camps.
By far the most economical and perhaps the closest to consensus choice is a modern Universal Tractor Transmission fluid (UTTF) for year round use in N-series, NAA, Hundred, and Thousand series tractors. It is a generic equivalent for Ford M2C-134D and a multi-function, multi-grade type lubricant designed for common sump tractors. It is the type of lubricant Ford starting recommending for all of these tractors in the early sixties.
From a technical standpoint it has the performance characteristics of both an SAE 70W80 GL-4 gear oil and a multi-grade (high VI) ISO 68 hydraulic oil. With a typical viscosity index of 130 and up it is an excellent cold weather hydraulic oil down to about 10F.