The viscosity of a fluid is its resistance to flow and is highly influenced by temperature. It decreases with rising temperature, i.e. the fluid becomes more liquid. The dependency of the kinematic viscosity on the temperature can be comparatively assessed by means of the viscosity index. Basically, it describes the change in viscosity with temperature.
The determination of the viscosity index is based on two oil types with the same starting viscosity and strongly diverging changes in viscosity as temperature rises. The oil showing a strong temperature dependence is assigned the viscosity index 0, whereas the oil with a lower change in viscosity is assigned the viscosity index 100. The viscosity index according to DIN 2909 is calculated by comparing the change in viscosity of an oil with the two oils as a reference.
Viscosity Index of lubricants
The viscosity of oils and base oils of lubricating greases from Klüber Lubrication can be determined by means of the known kinematic viscosity at 40 °C and 100 °C. The higher the viscosity index, the lower the viscosity change of an oil at fluctuating temperatures. A high viscosity index ensures consistent lubricating properties across a wide temperature range.