1、摩擦性能

1, the friction performance

一般要求润滑剂具有尽可能小的摩擦系数，保证机械运动敏捷而平稳，减少能耗。对于某些特殊机械，如液力传动系统、摩擦传动系统和摩擦制动系统，则要求有较高的摩擦系数。

General requirements of lubricant friction coefficient is as small as possible, to ensure the mechanical movement quickly and smoothly, reduce energy consumption. For some special machines, such as hydraulic transmission system, friction drive system and friction braking system, higher friction coefficient is required.

2、适宜的粘度

2. Suitable viscosity

粘度是液体润滑剂的最重要的性能，因此选择润滑剂时首先考虑粘度是否合适。高粘度易于形成动压油膜，油膜较厚，能支承较大负荷，防止磨损。但粘度太大，会造成摩擦热增大，摩擦面温度升高；而且在低温下不易流动，不利于低温启动。低粘度时，摩擦阻力小，能耗低，机械运动稳健，温升不高。但如粘度太低，则油膜太薄，承受负荷的能力小，易于磨损，且易渗漏流失，特别是容易渗入疲劳裂纹，加速疲劳扩展，从而加速疲劳磨损，降低机械零件寿命。

Viscosity is the most important property of liquid lubricant, so the choice of lubricant viscosity is appropriate when the first consideration. High viscosity is easy to form a dynamic pressure oil film, the film is thick, can support a larger load, to prevent wear. But the viscosity is too high, which will cause frictional heat to increase and the friction surface temperature to increase. Moreover, it is not easy to flow at low temperature and is not conducive to low temperature startup. Low viscosity, small friction resistance, low energy consumption, stable mechanical movement, temperature rise is not high. But if the viscosity too low, the oil film is too thin, the load bearing capacity is small, easy to wear and easy leakage, especially easy to penetrate the fatigue crack, accelerated fatigue growth, thus accelerating the fatigue wear, reduce the life of mechanical parts.

3、极压性

3, extreme pressure

处于边界润滑状态时，粘度作用不大，主要是靠边界膜强度支承载荷，因此要求润滑剂具有良好的极压性，以保证在边界润滑状态下，如启动时和低速重负荷时，仍有良好的润滑。

In boundary lubrication, the viscosity has little effect, mainly rely on the strength of the boundary film bearing load, thus requiring extreme pressure lubricant has good performance, to ensure that under boundary lubrication conditions, such as startup and low speed and heavy load, there is still a good lubrication.