Shock load: for example, the force of the engine made by the engine, which requires heavy oil to prevent the boundary lubrication produced by the instantaneous fragmentation of the oil film, because only a few lubricants can be left. In this case, a lubricant containing extreme pressure additive (EP) is needed.
Temperature: when the temperature drops, the lubricating oil will be thickened. When the temperature rises, it will become thinner. Therefore, low viscosity lubricating oil is needed at low temperature, and heavy oil is needed to prevent dry friction between metal and metal at high temperature.
Speed: the faster the speed of slip and rotation, the less time the gears will squeeze into the lubricant. At the same time, lubricants are thicker and thicker at high speed operation. Therefore, low viscosity should be used at high speed , heavy oil should be used at low speed.
Load (pressure): high viscosity oil is more resistant to heavy burdens than thin oil and prevents collisions between metal and metal. Therefore, light load requires low viscosity lubricants, high load requires high viscosity lubricants.
Gear type: the use of straight teeth, helical, herringbone and bevel gear pairs, sliding and rotation will produce effective oil film formation to slow the direct contact between the teeth of the meshing. The relative sliding operation direction of turbine shaft and hyperboloid gear is not conducive to maintaining oil film. The boundary lubrication often occurs on this transmission device. Therefore, heavy oil is still needed on the turbine turbine rod assembly and the large eccentric hyperbolic gear transmission. When the transmission is heavy and high pressure, it is necessary to choose the lubricating oil with high strength oil film characteristics (high viscosity), smoothness, lubricity, or even extreme pressure additive.