What is the most common ISO viscosity grade for hydraulic oil?

The ISO viscosity grade of 46 is commonly used for hydraulic oil due to its balanced performance characteristics across a wide range of operating temperatures and conditions. This viscosity grade strikes a practical balance between fluidity and film strength, making it suitable for most hydraulic systems. Hydraulic systems often operate at varying temperatures and loads, and oils with an ISO viscosity grade of 46 provide adequate lubrication, ensuring efficient operation and protection against wear in hydraulic components.

This viscosity grade facilitates optimal performance in hydraulic pumps and actuators by maintaining sufficient fluidity to prevent cavitation while also offering enough viscosity to maintain a protective film under pressure. Hydraulic oils need to offer proper viscosity at both cold start conditions and at elevated temperatures, and ISO 46 meets these needs effectively.

In comparison, other viscosity grades such as 100, 150, or 220 may be applicable in specific high-temperature or high-load scenarios, but they do not reflect the widespread application seen with ISO 46. Thus, this grade is preferred for its versatility and reliability in typical hydraulic applications.