The viscosity represents the strength of the oil film at a certain temperature.

The current driving test oil change index stipulates that when the viscosity of the oil at 100 ℃ exceeds ± 20%, the oil needs to be changed.

In actual operation, there is a trend of both increasing and decreasing oil viscosity.

The increase may be caused by the oxidation of the oil during use, which increases the overall viscosity. The decrease may be caused by the fracture of viscosity index improvers in multi-stage oils due to mechanical shear or diesel oil entering the oil system.

When the viscosity deviation exceeds ± 20%, it usually means that the composition of the lubricating oil has undergone significant changes and cannot effectively lubricate.

Therefore, lubricants on vehicle should be stopped and further inspection should be carried out to prevent damage to the vehicle.

During the development process of lubricant, in addition to passing bench tests, it also needs to undergo tens of thousands of kilometers of driving tests to confirm its stable and excellent performance.