In the daily maintenance of machinery, the condition of dimethyl silicone oil is of vital importance. As we all know, air is invisible and intangible, but it contains a lot of impurities. These impurities can cause the dimethyl silicone oil to deteriorate. To minimize the negative impact on the machinery caused by using deteriorated dimethyl silicone oil, we must always pay attention to the condition of the dimethyl silicone oil. But how exactly can we determine whether it needs to be replaced? Here are several practical methods. Firstly, the sunlight inspection method. On a sunny and clear day, gently pick up the dimethyl silicone oil with a screwdriver and make it form a 45-degree angle with the horizontal plane. Then, aim it at the sunlight and carefully observe the state of the oil droplets. Under the illumination of light, if you can clearly see that there are no abrasives in the oil droplets, it indicates that the dimethyl silicone oil is of good quality and can continue to be used normally; conversely, if you find that there are too many abrasives, it means that it can no longer meet the operating requirements of the machinery and should be replaced in time. Secondly, the finger rubbing identification method. Gently pinch the dimethyl silicone oil between the thumb and index finger and rub and grind it repeatedly. If the oil quality is excellent, the fingers can feel obvious lubricity, with few abrasives and almost no friction resistance. If you feel a strong gritty sensation between your fingers and the friction is significantly increased, it indicates that the impurity content in the oil is quite high and it is no longer suitable for continued use. It must be replaced immediately. Thirdly, the oil drop trace discrimination method. Prepare a clean white filter paper and drop a few drops of dimethyl silicone oil on it. Then, wait quietly for the silicone oil to seep. After the seepage process is completed, check the surface of the filter paper. If there is black powder and you feel a sense of blockage and roughness when touching it with your hand, it proves that the impurities in the oil have accumulated to a considerable extent. For high-quality dimethyl silicone oil, there should be no powder residue on the filter paper, and it feels dry and smooth when touched by hand, leaving only a faint yellow mark. Fourthly, the oil flow observation technique. Take two graduated cylinders. Pour the dimethyl silicone oil to be inspected into one of them, and leave the other empty on the desktop. Then, lift the graduated cylinder full of oil 30 to 40 centimeters away from the desktop and tilt it slowly to let the oil flow slowly into the empty cylinder. Pay close attention to the flow dynamics throughout the process. For high-quality dimethyl silicone oil, the flow should be slender, uniform and continuous. Once you find that the oil flow speed is uneven, sometimes with large chunks of oil pouring down, it indicates that the oil has deteriorated and needs to be replaced urgently.