The lubricating oil of deep groove ball bearing will be deteriorated and aged after a certain period of storage or use, and the lubricating effect will be lost seriously. This is due to the influence of many factors, such as mechanical shear, stirring, abrasive powder dust pollution, various gas effects, water or other oil penetration, thickening agent depolymerization, additive disappearance, temperature rise and so on. In order to ensure the lubrication effect and improve the service life of bearings, the oil should be replaced in time.
（1） Identification of deterioration degree of lubricating oil for deep groove ball bearing
The quality of lubricating oil can be judged and identified comprehensively and correctly only after collecting representative samples for testing and analyzing. In practical work, when the product has certain judgement experience, it can also be roughly divided from appearance, such as the increase of oil impurity, emulsification deterioration, foam accumulation and viscosity increase. All kinds of lubricating oil scrap index and oil change standard are formulated by domestic and foreign manufacturers, which are very important basis for the correct use of lubricating oil.
（2） Determination of oil renewal period
Generally, the replacement of lubricating oil mainly refers to the box type lubrication system. Due to the different service conditions and performance of various equipment, it is difficult to have a unified oil change cycle for the new oil. However, the physical and chemical indicators of the oil should be the measurement standard for oil replacement.