Oil viscosity determines both volumetric and mechanical efficiencies. It also sets the limits of the optimum operating range of a hydraulic system.

The energy loss due to friction in a fluid is due to its viscosity. When a fluid moves, a shear stress develops in it, the magnitude of which depends on the viscosity of the fluid.

What is oil viscosity

Viscosity is a measure of the thickness of the oil or its resistance to flow. Viscosity is perhaps the most important characteristic of hydraulic oil. Viscosity grade is measured in the Saybolt Second Universal (SSU) unit.

What is the oil viscosity index

What is oil viscosity

The ISO numbering of an oil is its viscosity grade at 40ºC. It means, for example, that an ISO 68 oil is an oil whose viscosity at 40°C is 68 cSt (±10%).

What does AW 68 mean?

The literal description of AW 68 is mineral oil with ISO 68 viscosity grade formulated with anti-wear additives, oxidation and corrosion inhibitors and demulsifiers for hydraulic systems operating at high pressures.

This class of hydraulic fluids can be used for heavy-duty hydraulic equipment such as industrial machinery gears, bearings, and pump bearings. However, it also has uses for:

  • Lubrication systems.
  • General lubrication.
  • Light duty reciprocating compressors.
  • High-pressure hydrostatic systems, in particular those with state-of-the-art vane and piston pumps.

How to choose the right hydraulic oil

How to choose the right hydraulic oil?

Choosing the right oil improves efficiency and reduces wear, allowing you to use less fuel and extend equipment life.

Here are the three essential qualities when selecting oil:

  1. Low or high oil viscosity index.
  2. With or without detergent.
  3. Anti-wear or non-anti-wear.