In Reply to: Re: Oils for 601 posted by Tim Daley(MI) on July 24, 2017 at 07:00:33:
The original Ford M-4864-A hydraulic oil specification is a mild EP (GL-4) gear oil, viscosity grade SAE 80. It was the Ford recommendation for all three sumps on a Hundred series. That is neither service category GL-1 or viscosity grade SAE 90.
In a Hundred series hydraulic system which is separate from the transmission and drive axle you also have the option of using a conventional AW type hydraulic oil. If you go that route an ISO 46 AW hydraulic oil will work fine as long as the sump seals are toght and there is no danger of it contaminating the other sumps. IMO a good guality UTF is a better choice and can be used also be used in the other sumps so leakage is not an issue. UTF is basically a grade 80 GL-4 gear oil with some additional additives for improved hydraulic and wet brake performance. At $40 for a 5 gallon pail it is hard to beat.