All parts, with the exception of a few items, are lubricated by the hydraulic oil in the circuit.
Particular attention must be paid to keep the oil in the circuit clean. Whenever there is a hydraulic
component failure (cylinder, pump, valve), and there is a reason to feel that metal particles may be 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.
Oil suitable and recommended for use in circuits involving pumps, motors and cylinders should meet the
Viscosity Index: 90 minimum
Aniline Point: 175 maximum
Recommended Additives: Foam depressant, rust
and oxidation inhibitors.
Filtration: 10 micron recommended for maximum
Normal Temperatures: Minimum Maximum
Ambient: O° F (-18° C.) 100° 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, sludges, acids, tars and varnishes.
• High lubricity and film strength.
A good quality hydraulic oil conforming to the characteristics listed above is essential to the
satisfactoryperformance 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.)
recommended. 120° F to 140° F. (50° C. to 60° C.) is generally considered the optimum system operating
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
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.