The type of hydraulic fluid recommended for a Massey Ferguson 471 tractor is 10W-30 engine oil. It should meet API (American Petroleum Institute) Service Classification SF/SG/SH, or API Certified CJ-4. When changing the hydraulic fluid, be sure to also replace the filter as well. If the tractor is used in extremely cold climates, it may be beneficial to use 5W-30 engine oil, meeting API specifications as mentioned above. If the tractor is used in very hot climates, 10W-30 oil may be too light and 15W-40 oil may provide better protection.