A hydraulic jack is a type of jack that cannot operate without oil, which is more time-consuming, labor-intensive, and fuel-efficient than a screw jack. However, it has a simple structure, is easy to carry, has strong lifting ability, and is easy to operate. Therefore, it is very suitable for work occasions such as automobile maintenance and bridge maintenance.

Frequent lifting, improper use, and poor sealing effect of hydraulic jacks can lead to a significant decrease in the internal oil volume of the hydraulic jack cylinder. When the internal oil volume decreases, it is necessary to add No. 42 hydraulic oil to it in a timely manner.

The method of oil injection is as follows: first, place the hydraulic jack steadily and slowly on the ground, with the plug of the oil injection hole facing upwards. After opening the plug, slowly pour oil into it. During the process of adding oil, we cannot visually judge the amount of oil, so we need to stand the jack upright and observe. If we find that the oil level of the jack is just level with the oil plug, we can stop adding oil. If it is not level, we need to continue adding oil.

It should be noted that when adding oil to hydraulic jacks, try to use specialized hydraulic oil instead of mechanical oil.