I have 4 fords (2)8N'S,NAA, an 860. It is time to change the hydraulic, Differential, and Transmission on all 4.They have been sitting in the barn awhile. I would like to use Gl-1 90 mineral oil but Tractor Supply doesn't carry it in 5 gallons anymore only in 2.5 gallon for $80. NAPA sells the 5 gallon for $148.These are western Pennsylvania prices. Any body know where to get it at a more reasonable price. The NAA uses a 134D oil in the Hydraulic but What oil is to be used in the differential and transmission or can I use 134D in all 3. The 860 owners manual suggests using the 134D in the hydraulic and 80 weight oil in the transmission and differential. Tractor Supply sells a 80-90 Weight oil in 5 gallon pails. Can I use this in place of the straight 80 weight. I would really welcome any useful suggestions about what fluids to use Where in these tractors These fluids are not cheap and I really hate to make a mistake which might harm the tractor. Thank you for taking the time to read this long entry.