TRANSMISSION FLUIDS
DO NOT use transmission fluids. These fluids have been designed to work in automatic
transmissions and they will not necessarily work in hydraulic systems.
MIXING:
Mixing different brands of oil is not recommended. Various companies use different
additive packages, which when mixed together, may cause problems in a hydraulic system.
This type of problem is rare but can cause sludge which can plug the filters or acid which
will etch the pump plates. In either case, the warranty would be voided. If, knowing all this,
you still choose to add oil different from the initial fill, stay with a single brand as this will
minimize the likelihood of problems occurring. Then at the first complete oil change you
may switch to the brand you prefer to use.
PRE-FILTER:
Oil should be filtered through a 10 micron nominal filter before it enters the hydraulic
system. New hydraulic fluid as received by the user is generally not in a satisfactory
cleanliness condition for long component life.
OIL MAINTENANCE:
Optimum life from hydraulic equipment can only be obtained with proper hydraulic oil
maintenance. This includes checking the oil every three to six months. An oil should be
checked for viscosity, oxidation, water content, contamination and copper particles. A
record should be kept of each check to detect signs of progressive deterioration. Oil
samples should be taken with the system running at normal operating temperature. It is
important to use good technique in obtaining an oil sample. The exact same procedure
should be followed each time an oil sample is taken. Most fluid suppliers will provide
assistance in analyzing your oil sample. The following are some guidelines to use in this
analysis.
Viscosity- Many hydraulic fluids will shear or thin out with use. The viscosity at each check
should be compared to the viscosity when new. At no time should the viscosity be less
than 45 SSU at 210° F. If viscosity is less than 45 SSU at 210° F, the oil must be replaced
immediately.
Oxidation- Oil oxidation will occur with age and use and is evidenced by a change in color
and/or odor, increased acidity, and possible formation of sludge, gum or varnish in the
system. The rate of oxidation increases significantly with operations at temperatures over
140° F (60°C). The oil should be checked more often if operation is a high temperature. The
oxidation process increases the acidity of the fluid and is measured by a neutralization
number. The oxidation process is typically slow at first and then increases sharply in the
final stages of complete oxidation. A sharp increase (by factor of 2 - 3) in a neutralization
number is a good indication that the fluid is reaching the limit of its oxidation life and should
be replaced.
Water Contamination- All hydraulic oils in the following charts will readily separate water
which will settle to the bottom of the reservoir. This water should be drained off. The water
T300-1_T500-1_T780
Maintenance
294 P/N 12261-683
REVISED: January 2015
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