Illumination method. On a sunny day, lift up the dimethylsilicone oil with a screwdriver at a 45 degree angle to the horizontal plane. Observe the condition of oil drop according to the sunlight. Under the light, it can be seen clearly that there is no wear debris in the oil, which is good and can continue to work. If there is too much debris, it should be replaced.

Oil flow observation method. Take two measuring cups, one of which contains dimethylsilicone oil to be inspected, and the other empty on the table top. Lift the measuring cup full of oil 30-40 cm away from the table top and tilt it. Let the oil flow slowly into the empty cup and observe its flow. The good quality should be the slender oil flow observation method. Take two measuring cups, one of which is filled with dimethylsilicone oil to be inspected, and the other is empty on the table top. Lift the measuring cup full of oil 30-40 cm away from the table top and tilt it to let the oil flow slowly into the empty cup. Observe the flow situation. The good quality should be slender, uniform and continuous. If the oil flows fast and slowly, and sometimes large pieces flow down, it is said that it has deteriorated.

Hand twisting. When the dimethylsilicone oil is twisted between the thumb and the index finger for repeated grinding, the hands with better quality feel lubricity, less wear debris and no friction. If the greater friction feeling such as sand grains between fingers is felt, it indicates that there are many impurities in the oil and can not be used again, so it should be replaced.