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Discover the CITGO Difference

CITGO Hydraulic Fluids

Used to transmit power, the heart of any hydraulic system is a hydraulic pump. Keeping the pump, as well as other components, working at peak performance during high loads, hydraulic fluids must be kept at the recommended levels and must be changed periodically. Avoid lack of lubrication or noisy pumps by using high-quality hydraulic fluid in your hydraulic system.

Purpose of Hydraulic Fluids
The blood of a hydraulic system, hydraulic fluid transmits power. It also seals parts against leakage, minimizes wear, removes heat, and flushes dirt particles away. Conventional petroleum oils are normally used in a hydraulic system, but synthetic, fire-resistant, and biodegradable fluids are also used.

Hydraulic Efficiency
Within a hydraulic system, the fluid temperature can vary widely. Significantly impacting the viscosity and stability of a fluid, wide changes in ambient temperature can make seasonal changes in viscosity grade necessary. Keeping a hydraulic system in top shape, and using high-quality fluids ensures the continued efficiency of a hydraulic system. Using a high viscosity index fluid can make seasonal fluid changes a thing of the past.

Hydraulic Care and Maintenance
In a high pressure system, routine care and maintenance of the system is important. New systems should be flushed before fluid is added. To prevent contamination, good storage and handling practices should be utilized when working with hydraulic fluids. Store fluid in a protected area and dispense it only in clean containers. Always filter the fluid just as it is being introduced to the system.

Hydraulic Temperatures
The high temperatures generated in high pressure hydraulic systems can cause hydraulic fluid to oxidize. Oxidation leads to varnish and sludge deposits. In contrast, low temperatures can cause condensation to develop in the reservoir and increase the possibility of rust forming on interior reservoir surfaces. It is important to determine the operating temperature range for your hydraulic system and select a fluid of appropriate viscosity grade and viscosity index to cover that range.

Fluid Analysis
Most hydraulic systems require regular monitoring. For large volume systems, annual or semi-annual checks are recommended. For critical machines, quarterly or monthly checks are typical. With a fluid analysis program, it is possible to increase the service life of hydraulic fluid and monitor for early warning signs of mechanical problems or fluid degradation. Consulting with a lubrication engineer or hydraulic fluid expert is the best way to learn more about fluid analysis programs.

Fluid Change-Out
There are several proper steps to follow when changing the fluid in a hydraulic system. Following these steps will ensure the fluid is changed quickly and safely. The steps include:

  1. While the fluid is still at operating temperature, drain the system.
  2. Empty fluid from cylinders, accumulators, and lines that may not have drained, such as low points in piping systems. Air blowing lines may be required.
  3. Siphon or pump out any residual oil left in the reservoir.
  4. Wipe the reservoir clean and remove any rust that may be on internal reservoir surfaces.
  5. Replace or clean filter elements.
  6. While venting at high points, refill the system with new fluid.
  7. Restart the system and confirm satisfactory operation.


It is important to shut down and deenergize a hydraulic system before interacting with it. This includes allowing pressure to be relieved to the system reservoir. Hydraulic systems work under high pressure and spray from any high pressure leak can cause serious injuries. Pumps, valves, and the motor may become very hot. Be aware of the temperature ranges common to a hydraulic system and avoid contact between bare skin and hot surfaces. Hands and clothing must also be kept away from any moving parts. Always wear appropriate personal protective equipment (PPE).

With high loads and high pressure, a hydraulic system depends on hydraulic fluids for operational efficiency. Choosing the right fluid and conducting fluid analysis, along with fluid change-outs based on oil condition monitoring, ensures the extended life of a system. To maintain a hydraulic system, its parts and components, choose from a variety of available hydraulic fluids.

LubeAlert Fluid Condition Monitoring Service

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