Kinematic Viscosity

Kinematic Viscosity



The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the informal notion of "thickness". For example, honey has a higher viscosity than water.

Viscosity is due to friction between neighboring parcels of the fluid that are moving at different velocities. When fluid is forced through a tube, the fluid generally moves faster near the axis and very slowly near the walls, therefore some stress (such as a pressure difference between the two ends of the tube) is needed to overcome the friction between layers and keep the fluid moving. For the same velocity pattern, the stress required is proportional to the fluid’s viscosity. A liquid’s viscosity depends on the size and shape of its particles and the attractions between the particles.

A fluid that has no resistance to shear stress is known as an ideal fluid or inviscid fluid. Zero viscosity is observed only at very low temperatures, in superfluids. Otherwise all fluids have positive viscosity. If the viscosity is very high, for instance in pitch, the fluid will appear to be a solid in the short term. A liquid whose viscosity is less than that of water is sometimes known as a mobile liquid, while a substance with a viscosity substantially greater than water is called a viscous liquid.

Why we need to know?

  • The resistance of a substance to flow. For example, water has a lower viscosity than molasses and flows more easily. Viscosity is related to the concept of shear force; it can be understood as the effect of different layers of the fluid exerting shearing force on each other, or on other surfaces, as they move against each other. Viscosity lies behind the skin friction component of drag. Kinematic viscosity is a measure of the rate at which momentum is transferred through a fluid. It is measured in stokes. Dynamic viscosity is a measure of the ratio of the stress on a region of a fluid to the rate of change of strain it undergoes. It is equal to the kinematic viscosity times the density of the fluid. It is measured in pascal-seconds or posies.
  • The viscosity of many petroleum fuels is important for the estimation of optimum storage, handling, and operational conditions. Thus, the accurate determination of viscosity is essential to many product specifications.

Viscosity for General Oil and Pentas Flora Recovered Oil:

General Oil

Viscosity (cSt)

Base Oil


Bunker Fuel

> 200



Heavy Oil

> 200

Light Fuel Oil 80 cSt

66 – 88

Medium Fuel Oil 180 cSt

> 180

Tyre Oil


Waste Engine Oil

35 – 45

Pentas Flora Recovered Oil

Viscosity (cSt)

Eco Light Fuel Oil

 18 – 20

Super Light Fuel Oil

6 – 10

Green Light Fuel Oil

70 – 80

Base Light Fuel Oil

 40 – 50