Characteristics Of Quality Hydraulic Fluids

Be sure to consider equipment requirements as well as fluid prices when choosing hydraulic fluids

Characteristics of Quality Hydraulic Fluids

Hydraulic equipment is useless without quality hydraulic fluid. Because hydraulic fluid is the most important component of any hydraulic system, it is very important that you understand how to recognize the characteristics of high-quality hydraulic fluids. If you keep the following considerations in mind when shopping for hydraulic fluids, you will soon find the ideal hydraulic fluid for your needs.

Characteristics of quality hydraulic fluid

Quality hydraulic fluid will help your hydraulic equipment to run more smoothly and efficiently. Characteristics of high-quality hydraulic fluids include the following:

  • Thermal stability
  • Low chemical corrosiveness
  • Hydrolytic stability
  • Low tendency to cavitate
  • Total water rejection
  • Long life
  • High anti-wear properties
  • Low cost
  • Constant viscosity

Although no single hydraulic fluid will have all of the above characteristics, you can pick and choose the hydraulic fluids that have the most beneficial characteristics for your particular hydraulic system.

Characteristics of hydraulic systems

In order for you to choose the hydraulic fluid with the characteristics that best suit the needs of your hydraulic system, you will first need to understand the basic characteristics of your hydraulic system. Important hydraulic system characteristics include:

  • Type of pump(s) used
  • Operating cycle
  • Type of power and control valves
  • Operating pressures
  • Ambient temperatures
  • Minimum and maximum operating temperatures

Understanding your hydraulic system’s unique characteristics will help you to choose a hydraulic fluid that matches perfectly.

Hydraulic fluid performance factors

There are several factors that influence the way hydraulic fluid performs, including:

  • Viscosity
  • Wear
  • Corrosion
  • Fire resistance

While the above list is not all-inclusive, it does mention some of the most important factors that can influence hydraulic fluid performance.


Hydraulic fluid’s viscosity requirements are determined by the hydraulic system’s load as well as its minimum and maximum operating temperatures. The right hydraulic fluid for your hydraulic system will need to maintain a minimum viscosity even at the hottest operating temperature, but it must not be too viscous to pump at low temperatures.


Wear affects the moving parts of hydraulic systems and occurs when metal contacts metal. A good hydraulic fluid will help reduce wear by lubricating moving parts and providing a thin layer of protective oil.


Corrosion of hydraulic system components is usually caused by acidic chemical corrosion, system rusting, or both. A good hydraulic fluid should have rust inhibitors and other additives that protect against corrosion and rusting.

Fire resistance

An important characteristic of some hydraulic fluids is fire resistance. This is especially important if your hydraulic system works at extremely high temperatures, or if it is placed in a flammable environment. To keep yourself and those around you safe, consider purchasing fire resistant hydraulic fluids.

To find out more about important characteristics of hydraulic fluids, visit Bernell Hydraulics at

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