1. Light method
Under the light, observe the oil situation, if can see clearly without wear debris in lubricating oil, so is good, can continue to use; If there is too much abrasive dust, the lubricating oil should be replaced.
2. Oil drop trace method
Drops of oil on the filter paper, after the lubricating oil leaks, if there is black powder on the surface, and there is a feeling of astringency when touched by hand, it means that there are a lot of impurities in the lubricating oil.
3. Oil flow observation method
Lift the measuring cup filled with lubricating oil from the table 30-40 cm and tilt, let the lubricating oil slowly flow into the empty cup, good quality lubricating oil should be slender and uniform when flowing, if the oil flow is fast and slow, it is said that the lubricating oil has deteriorated.
4. Hand twist method
The lubricating oil is twisted between the thumb and index finger repeatedly grinding, the better lubricating oil hand feels lubricity, less grinding chips, no friction, if you feel the sand between the fingers such as a greater sense of friction, it indicates that the lubricating oil is more impurities, can not be used again, should be replaced with new lubricating oil.
