What is the viscosity-temperature performance of lubricating oil?


Release time:

2022-01-10

The viscosity of lubricating oil, in layman's terms, indicates the degree of thinning of lubricating oil. The thicker lubricating oil has poor fluidity, which will cause a lot of energy loss in overcoming the internal resistance of the lubricating oil, but it can form a thicker lubricating film on the surface of the machine,so it is suitable for working at higher temperature, heavy load and lower speed . Conversely, Conversely, thinner engine oil forms a thinner oil film, but has good fluidity and low resistance, but it has good fluidity and low resistance, it’s suitable for working at low temperature, low load and higher speed.

The viscosity of the lubricating oil varies with temperature. We all have this experience: a barrel of oil will feel it thicken in cold weather, and we will feel it thin in hot weather. The characteristic that the viscosity of lubricating oil changes with temperature is called the viscosity-temperature performance of lubricating oil, and the quantitative index of this characteristic is called the viscosity index of lubricating oil.

According to the different viscosity index, lubricating oil can be divided into three levels: 35-80 for low viscosity index lubricating oil; 80-110 for high viscosity index lubricating oil; viscosity index of more than 110 is the high viscosity index of lubricating oil. Now the engine oil used on cars is required to be ultra-high viscosity index lubricating oil. For example, the viscosity index of Great Wall Jingixing SL 5W-40 is 172, while that of Great Wall Jingixing SM/CF 0W-50 is higher. The higher the viscosity index means the smaller the change in oil viscosity with temperature, and the wider the adaptation range to temperature.That is, low temperature (below zero) has good fluidity, easy to start and good cold start protection;. That is, low temperature (below zero) has good fluidity, easy to start and good cold start protection; when the engine temperature is high or the ambient temperature is high (for example: the desert surface temperature reaches 70 degrees), the oil viscosity will not drop significantly, and it can still be effective protect the engine.