The function of the power element is to convert the mechanical energy of the prime mover into the pressure energy of the liquid, and the oil pump in the hydraulic system, which provides the power for the whole hydraulic system. Hydraulic pump in the structure of the general form of gear pump, vane pump and piston pump.

Lubrication oil (abrasion resistance) on the three pump friction reducing effect order of vane pump plunger pump, gear pump. Vane pump main pump hydraulic system regardless of the size of the pressure is appropriate selection of HM oil as well, because between the vane pump vane and stator contact and movement form easy to wear, the steel on steel friction pair material is most suitable for use of high zinc HM anti-wear hydraulic oil.

For low pressure piston pump available HM oil and HL oil, high-pressure plunger pump with zinc HM oil but when piston pump in bronze and silver plated parts, high zinc anti-wear agent will produce corrosion wear, the plunger pump to use low ash or zinc anti-wear hydraulic oil.

Generally, HL oil can be preferentially used for axial piston pump, but it is not suitable for vane pump, high zinc HM oil is suitable for all kinds of vane pump. The ash free HM oil is suitable for axial piston pumps with copper and silver parts, and is suitable for medium and low pressure vane pumps, but not for high pressure vane pumps. Low zinc HM oil is of wide application range, is suitable for medium and high pressure vane pump, plunger pump is suitable for copper and copper parts.

Hydraulic oil service life (i.e. oil change period) because of variety of hydraulic oil selection, working environment and system operating conditions are different, and have bigger difference, elected reasonable oil, oil quality excellent, hydraulic system and hydraulic oil has good maintenance and management, oil change period can be greatly extended.