1. Moisture content
Combustion method. Dip a small amount of the oil to be tested with clean and dry cotton yarn or paper, and then ignite it with fire. If there is a cracking sound or flashing phenomenon, it indicates that the oil contains a lot of water.

2. Impurity content
Filter paper detection. For hydraulic oil with high viscosity, it can be diluted with pure gasoline and filtered with clean filter paper. If a large amount of mechanical impurities (metal powder) are found on the filter paper, it indicates that the hydraulic components have been severely worn.

3. Viscosity
Glass plate tilting method. After using the machine for a period of time, if it is deemed that the viscosity of its hydraulic oil does not meet the requirements and a new oil needs to be replaced, a clean glass plate can be taken and placed horizontally. One drop of the tested hydraulic oil should be dropped on the glass plate, while another drop of standard hydraulic oil (new hydraulic oil of the same brand) should be dropped next to it. Then, the glass plate should be tilted and observed carefully. If the flow rate and flow distance of the measured oil are greater than those of the standard oil, it indicates that its viscosity is lower than that of the standard oil; On the contrary, it indicates that its viscosity is higher than that of standard oil.