Oil drop trace method: Take a piece of clean white filter paper and put a few drops of grease on the filter paper. After the grease leaks, if there is black powder on the surface and a sticky feeling when touched with your hands, it means there is something inside the grease. There are already a lot of impurities. A good grease has no powder, feels dry and smooth to the touch, and has yellow marks.

Oil flow observation method: Take two measuring cups, one of which contains the grease to be inspected, and place the other empty on the table. Lift the measuring cup filled with grease 30 to 40 cm away from the table and tilt it to allow the grease to flow slowly. Slowly flow into the empty cup and observe the flow. Good-quality grease should flow in a slender, even, and continuous flow. If the oil flow appears to be fast and slow, and sometimes large chunks flow down, it means that the grease has deteriorated. .

Lighting method: On a sunny day, use a screwdriver to lift up the grease and make it at a 45-degree angle to the horizontal plane. Observe the oil droplets against the sunlight. Under the light, you can clearly see that there is no wear debris in the grease, which means it is good and can continue to function. If there is too much wear debris, the grease should be replaced.