In Reply to: Re: 90 WT Mineral Oil posted by mthomas on March 28, 2018 at 09:47:26:
Short answer, use UTF.
Long answer............the owner’s manual was written in the early 1950’s. Just like with engine oil, much has changed for the better in petroleum products in the past 60 years. The original recommendation was EP Gear Oil conforming to Ford specification M-4864-A and B, SAE 80 below +32 degrees F, and SAE 90 above +32 degrees F. (Do you want to change your hydraulic fluid every spring and fall? ) However, the new recommendation from the local Ford-New Holland dealer now recommends Ambra Multi-G 134 (NH-410B) synthetic fluid. Some people stick with the original spec and use 90w mineral oil. The modern equivalent of 90w mineral oil is TSC Traveler brand GL-1 or NAPA part number 65-205. Those may be less expensive, but the Multi-G 134 synthetic is good from -5 to 120 degrees F! CNH sells a product called Ambra 134D that conforms to that specification. The equivalent product (and less expensive) from TSC that meets Ford spec M2C-134d is their Universal Tractor Fluid. Neither of these products are SAE 90 gear oil - they are multi-purpose oils with an exceptionally high viscosity index engineered specifically for this type of application. The TSC product labeled "Ford Tractor Oil" is a plain SAE 90 gear oil.