1. Extremely low vapor pressure  

This is the most critical performance characteristic of vacuum pump oil. Since vacuum pumps require very high vacuum levels, paraffin-based narrow-distillation lubricating oils are typically used. For diffusion vacuum pumps, silicone oils or other synthetic oils with extremely low vapor pressure can also be employed.  

2. Appropriate viscosity and excellent viscosity-temperature characteristics  

The volume within the vacuum pump chamber continuously changes to create an exhaust effect, necessitating that the lubricating oil possess appropriate viscosity and viscosity-temperature characteristics.

3. Excellent thermal and oxidative stability  

As vacuum pumps continue to evolve toward higher speeds, the high-speed friction between the sliding vanes and the pump body causes oil temperature to rise, leading to easy oxidation and decomposition of the oil. Especially for diffusion pumps, which often operate in high-temperature environments, this can cause the vapor pressure within the system to increase, resulting in reduced vacuum levels. Therefore, vacuum pump oil must possess excellent thermal and oxidative stability.

4. Good corrosion resistance and anti-emulsification properties  

If the vacuum pump inhales corrosive gases, they may react chemically with the oil, corroding internal components. Air often contains water vapor and condensation, which can cause the vacuum pump oil to emulsify and corrode metal parts. Therefore, the oil must have good corrosion resistance and anti-emulsification properties.  

5. High flash point  

The primary requirement is that the vacuum pump should not carry light components to avoid affecting the oil's saturated vapor pressure.