How to choose hydraulic oil for cross-stacker

How to choose hydraulic oil for straddle stackers ?The hydraulic system should be filled with new cleaning oil. If the hydraulic oil is not clean, will affect the precision of hydraulic components, so that the entire hydraulic system capacity. If the use of different grades of hydraulic oil, damage to the semi electric stackers, but also affect the system capacity. Therefore, pay attention to the use of the same grade when adding or replacing hydraulic fluid.