How to check the quality of lubricating oil used in the universal testing machine

How to check the quality of lubricating oil used in the universal testing machine, mainly judged through the following four aspects:
(1) Appearance (color) The color of the oil product can often reflect its degree of refinement and stability;
(2) The viscosity reflects the internal friction of the oil product and is an indicator that indicates the oil quality and fluidity of the oil product;
(3) Viscosity index The viscosity index represents the degree to which the viscosity of the oil product changes with temperature;
(4) Density density is a simple and commonly used physical performance indicator for lubricating oil.