What oil does the traditional anchor oil cup add?

Traditional bolt oil cup with hydraulic oil.

The most important factor to consider when selecting hydraulic oil is its viscosity. If the viscosity is too high, the pressure loss and heat production of the liquid flow will be great, which will reduce the efficiency of the system; If the viscosity is too small, the increase of leakage will also affect the system efficiency. Therefore, it has suitable viscosity and good viscosity-temperature characteristics.