Information on the operating viscosity characterises the viscosity range in which the entire system can operate. A differentiation is made between three key figures:
Maximum start viscosity:
Characterises the still just permissible viscosity limit and with it the lowest temperature at which the system can still just be operated. A higher viscosity will cause cavitation to occur in the pump.
Minimum operating viscosity:
Is defined by the reduction in the lubrication properties and the increase in the leakage losses with excessively thin oil. It marks the upper temperature of the oil that is just permissible.
Maximum operating viscosity:
Is limited by the permissible viscosity of the other devices in the system (e.g. valves) as well as by the time it takes air bubbles to rise.
Together with the min. operating viscosity, the oil temperature range in which the system is fully functional is characterised.