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A petroleum kinematic viscosity tester is used to measure viscosity when a liquid moves in laminar flow as a result of external forces; that is, the particles in the fluid move in an orderly manner, without mixing with or interfering with each other, and move in layers or streams. Frictional resistance exists between the liquid molecules, which is why the liquid possesses a certain degree of viscosity. Purpose of use ◆ Viscosity can determine the processing conditions, define the range for fractionation, and assess the degree of refinement of lubricating oil. In lubricant refining, the more polyyclic short-side-chain polycyclic aromatic hydrocarbons and gums that are removed, the lower the viscosity of the refined oil. Generally, the viscosity of unrefined distillate oil is > the viscosity of distillate oil refined with sulfuric acid > the viscosity of distillate oil refined with a selective solvent. ◆ Viscosity is one of the important indicators of jet fuel. Since the viscosity of jet fuel has a significant impact on the degree of fuel atomization, and the quality of fuel atomization determines the required level of atomization for jet engines at different temperatures, jet fuel specifications specify viscosity requirements at 20°C and -40°C. ◆ Viscosity is one of the important properties of diesel; it determines how well diesel atomizes and burns within an internal combustion engine. If the viscosity is too high, the oil droplets ejected by the injector are large, resulting in poor atomization, inadequate mixing with air, and incomplete combustion, which affects the engine’s power output ； Too low viscosity leads to easy evaporation and significant losses; it also affects the lubrication of the oil pump and increases wear on the seals. ◆ Viscosity is an important quality parameter for lubricants; using lubricants with too high a viscosity can reduce the engine’s power, increase fuel consumption, and also make it difficult to start the engine. If a lubricant with too low viscosity is used, it becomes difficult to form an oil film at the lubricated area, resulting in \"dry friction\" between the two frictioning surfaces; this fails to achieve the purpose of lubrication and increases wear on the machine. The grades of lubricating oils are mostly classified in product standards based on the average dynamic viscosity. For example, refrigeration oils and machine oils are classified according to the average centistokes value of their dynamic viscosity at 50°C, while engine lubricants, cylinder oils, gear oils, etc., are classified based on the average stokes value of their dynamic viscosity at 100°C. Selecting a lubricant with the appropriate viscosity ensures that its functions are fully utilized, thereby maintaining the engine in a stable and reliable operating condition. Excessively high viscosity can cause difficulty in starting the engine. Increase the consumption of anti-knock fuel and reduce engine power ； If the viscosity is too low, it will reduce the supporting capacity of the oil film, preventing a continuous lubricating layer from being maintained between the friction surfaces and increasing component wear.