In Reply to: Hydraulic Fluid Source posted by Richard on February 24, 2019 at 12:55:43:
That is a 60+ year old Ford specification with no known (to me) documentation of its properties. At best we know from usage guidelines it had a lower viscosity than SAE 80 gear oil. I suggest you go get a few gallons of quality AW-46 hydraulic oil - it should perform better than the M-4864D oil ever did. If you are going to be using the loader in temperatures approaching 0F you might consider going one grade lighter - AW-32. A good alternative for year round use woyl be a modern Universal Tractor Transmssion fluid which can also be used in the transmission and final drive of older Ford tractors. All of those oils are available at just about every auto and tractor parts supply house.