Hydraulic fluid is a liquid substance used to transmit power in hydraulic systems. It has various properties that affect its performance, such as viscosity, flash point, pour point, and oxidation stability. Viscosity determines the fluid's ability to flow through the system and affects its power transmission capacity. Flash point and pour point indicate the fluid's flammability and low-temperature performance, respectively. Oxidation stability is important for maintaining the Hydraulic fluid properties. Proper selection and maintenance of hydraulic fluid is crucial for the reliable and efficient operation of hydraulic systems.