How do you choose the right hydraulic fluid?

The viscosity (or thickness) of the hydraulic fluid is the most important parameter. It affects almost everything: from efficiency to the service life of the pump.

• Too low viscosity → thin oil film, more friction and wear, risk of internal leaks.
• Too high viscosity → slow operation, more energy loss, risk of cavitation and overheating.

The correct viscosity depends on the temperature, load and design of the system. A good hydraulic oil maintains its viscosity over a wide temperature range, ensuring stable performance.

In addition to viscosity, other properties also play a role in the choice of your hydraulic oil:

• Anti-wear additives (AW): protect metal surfaces from direct contact. There are zinc-containing (ZDDP) and zinc-free variants.
• Viscosity index (VI): the higher the index, the more stable the oil remains during temperature fluctuations.
• Oxidation and thermal stability: prevents oil from ageing or forming deposits at high temperatures.
• Ventilation & foaming: air in the oil reduces efficiency and causes cavitation.
• Filterability: determines how easily oil flows through filters without hindering performance.
• Water separation capacity: important in humid environments to prevent corrosion.
• Compatibility: ensure that the oil is compatible with the seals, hoses and materials used.

When selecting a hydraulic fluid, you can follow these steps:

• Determine the correct viscosity for the operating temperatures of your installation.
• Choose suitable additives: zinc-containing or zinc-free, depending on the application and environmental requirements.
• Pay attention to the viscosity index (VI): choose a high VI for applications with large temperature fluctuations.
• Manage contamination: keep an eye on filters and oil condition for a longer service life.
• Check the regulations: in some applications, geographical areas or industrial environments, fire-resistant or biodegradable oils are mandatory.

Choosing the right hydraulic fluid is more than a technical decision. It is an investment in efficiency, reliability and sustainability.
By taking into account the specific requirements of your hydraulic system and the environment, you not only extend the service life of your components, but also reduce the risk of malfunctions.