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The viscosity of the oil
| Fig. 6.1. The viscosity of the motor oil
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The viscosity of the oil's flow properties, which depends on the temperature. With increasing temperature, the oil becomes more fluid. This worsens the oil's ability to form a film on the metal and to withstand the high contact pressure. When cooling oil gets denser, fluidity decreases and increases the internal friction. The engine must be used engine oil of a certain viscosity, which depends on the construction, the operation mode, the degree of wear, ambient temperature and other factors. When starting a cold engine oil should be sufficiently liquid in order not to unduly overload the starter. Furthermore, after starting it should rapidly penetrate to all lubrication points. Oil viscosity is expressed in units - the viscosity index SAE (Society of Automotive Engineers - Association of Automotive Engineers USA), such as SAE 30, SAE 10. High indicator SAE corresponds oil with high viscosity, low characterizes liquid oil.
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