Viscosity
General
Viscosity is a measurement of the internal friction of the oil or of its resistance to flow. It does not however give any indication as to the quality of the oil, but is nevertheless perhaps the most significant characteristic of a lubricating oil. The viscosity of the oil should be adapted so that at operating temperature it retains its lubricity between surfaces, irrespective of the amount of loading. The viscosity should not therefore be too high as this causes increased bearing friction and power loss. The viscosity of a liquid is an expression of the product's resistance to flow, or as stated earlier, a measurement of its internal friction. All fluids becomes thinner when heated and as a result the determining of a viscosity must be carried out at given temperatures, for example, 20, 50, 100 or 150 degrees.
The viscosity can be divided up into two categories, dynamic and kinematic.
