If you bought SAE 30 oil, for example, it had a kinematic viscosity of 30 at a temperature of 100В° C (212В° F). They had only one viscosity rating that was based on their kinematic viscosity at 100В° C (212В° F). Now we suggest you take a look at the article Understanding Kinematic Viscosity to get to grips with what Kinematic Viscosity means. Once upon a time, all motor oils were single-viscosity or 'straight weight' oils. Water is a low viscosity fluid syrup is a high viscosity fluid. It is the single most critical physical property of the oil as it affects both the wear rate and the fuel efficiency. However when the oil is made into a grease things change, the grease would be non-Newtonian, a grease viscosity being highly dependent on the rate of shear, or the rate at which the adjacent layers of grease move relative to one another. Viscosity, by definition, is an oilвЂ™s resistance to flow and shear. Oil with a viscosity that does not change much between the temperatures of 40вЊ and 100вЊ has a higher VI than an oil with a relatively higher change in viscosity. Simple fluids including most lubricating oils follow Newtonian behaviour whereby fluid viscosity remains constant as a function of shear rate. We can change the apparent viscosity of a finished grease by altering the ratio of thickener to base oil.

A grease is created when a thickener is added to a base oil giving a lubricant the вЂstay in placeвЂ™ characteristics familiar with a grease. Oil viscosity can vary and we wanted to show just how big the differences can be. With the right additives to help it resist thinning too much in the heat, an oil can be rated for one viscosity when cold and another viscosity when hot.

This test was conducted at room temperature.

We decided to make it easier with a video explanation so our customers can better understand the centistoke (cSt) numbers on a data sheet. When selecting a synthetic grease for a customer, we often discuss oil viscosity and the implications of higher and lower base oil for their application.