## Hydraulic oil viscosity

Summary:

- Dynamic and kinematic viscosity in SI and British unit
- Understanding the optimum operating viscosity range
- Selecting the ISO VG (Viscosity Grade) for your system
- Understanding the Viscosity Index

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The viscosity is a measure of the fluid’s resistance to flow.

There are **dynamic** and **kinematic** viscosity are usually common for calculations.

The symbol for dynamic viscosity is the Greek letter mu (µ). The SI unit for dynamic viscosity is the pascal-second (Pa·s), but the more common unit is the **centipoise** (cP):

1 P = 0.1 Pa·s

1 cP = 0.001 Pa·s = 0.001 N·s/m^{2}.

For example, the dynamic viscosity of water at 20°C is 1.00 cP