Hydraulic Oil Recommendations

All parts, with the exception of a few, are lubricated by the hydraulic oil in the circuit. Pay particular attention to keeping oil in the circuit clean. Whenever there is a hydraulic component failure (cylinder, pump, valve), and there may be metal particles in the system, the oil must be drained, the entire system flushed clean, and any filter screens thoroughly cleaned or replaced. New oil should be supplied for the entire system.

Recommended oil suitable for circuits involving pumps, motors and cylinders should meet the following specifications:

Viscosity Index: 90 minimum
Aniline Point: 175 maximum
Recommended Additives: Foam depressant, rust and oxidation inhibitors.
Filtration: 10 micron recommended for maximum pump life.

Normal Temperatures Minimum Maximum
Ambient 0° F (-18° C.) 100dfs° F.   (37.8° C.)
System 100° F. (37.8° C.) 180° F. (82.2° C.)


Other Desirable Characteristics:

  • Stability of physical and chemical characteristics.
  • High demulsibility (low emulsibility) for separation of water, air and contaminants.
  • Resistant to the formation of gums, sludge’s, acids, tars and varnishes.
  • High lubricity and film strength.

General Hydraulic Oil Recommendations :

  • Essential characteristics above make good quality hydraulic oil needed for satisfactory performance and long life of any hydraulic system.
  • Oil should be changed on regular schedules in accordance with the manufacturers recommendations and the system periodically flushed.
  • Oil operating temperature should not exceed 200° F. (93° C.) with a maximum of 180° F. (82° C.) generally
  • recommended. 120° F to 140° F. (50° C. to 60° C.) is generally considered the optimum system operating temperatures. High temperatures result in rapid oil deterioration and may point out a need for an oil cooler or a larger reservoir. The nearer to optimum temperature, the longer the service life of the oil and the hydraulic components.
  • The system reservoir capacity should equal, in gallons, the pump output in gpm or the total gpm of all pumps where there is more than one in the system.
  • Oil poured into the reservoir should pass through a 100 mesh screen. Pour only clean oil from clean containers into the reservoir.
Viscosity @ 100 deg. F. 150 SSU Minimum D88
Viscosity @ 210 deg. F. 42 SSU Minimum D88
Viscosity index 95-125 D2270
Gravity, API 28.9-31.0 D287
Zinc .08% Minimum By Weight
Corrosion at 212 deg. F. Maximum 1 D130
Emulsion at 130 deg. F. 30 D1401
Flash point deg. F. Minimum 380 D92
Foam Test:    
Tendency @ 75 deg. F., M1 , Maximum 75 D892-IP146
Stability @ 75 deg. F., M1, Maximum    
Pour Point deg. F., Minimum* -20 D97
Rust Test -Pass D665
Minimum Hours to reach Acid No.2 2,000 D943