These pumps are designed to work with specific types of hydraulic fluids. The recommended hydraulic fluid should have appropriate viscosity, anti-wear, and anti-oxidation properties. The suitable viscosity range of the hydraulic fluid is usually between 10 - 400 cSt (centistokes) at the operating temperature range of the pumps, which is generally from - 20°C to + 80°C (- 4°F to 176°F).