Understanding Kinematic Viscosity

Kinematic Viscosity (KV) is a type of viscosity data point that you will see on all our synthetic lubricant technical data sheets. There are different ways to measure the viscosity of a lubricant as the subject matter is not simple. Kinematic Viscosity is an oil/fluid resistance to flow under the influence of gravity – no external force is applied, only gravity is influencing the oil/fluid.

Depending on the temperature requirements for a specific application, it is important to understand the change in viscosity of an oil as temperature drops, which also gives an insight into what will happen when the oil is worked, in kinetic sense – Penetration Testing is a better data point to understand what happens to a finished grease from a kinetic energy standpoint.

The unit of measurement we use for KV is Centistokes (cSt). Other companies sometimes use m2/s. Here is an example of KV data on from a Polyalphaolefin base oil:

KV is an important data point but if using a grease, it is crucial to remember that kinematic viscosity only relates to the base oil within the grease. This does not detract from the importance of KV as the KV of the base oil will influence the finished grease stiffness/thickness and how the grease responds under the effects of shear; another example is when a grease is used in bearing applications, under pressure and load it is the grease that is forced away from the thickener of the grease that is ofter performing the lubrication task.

Especially in mechanical lubrication applications. The KV characteristics and the resulting film strength of a lubricant are important to understand as is the chemical structure of a base oil/fluid.

Take a look at our video base oil viscosity demonstration video to see what different cSt fluids look like at room temperature and maybe look also at our base oil overviews to understand some of the chemistry we work with.

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