Which metric matters for low-temperature grease
The most common mistake is looking only at pour point. Pour point only tells the lowest temperature at which the oil still flows, but what actually decides low-temperature usability is low-temperature starting torque and low-temperature penetration — whether the grease hardens, seizes or adds too much starting resistance in the cold.
Key metrics
- Low-temperature starting torque: how much force is needed to start the bearing when cold — the lower the better;
- Low-temperature penetration: grease softness at low temperature, directly reflecting flowability;
- Pour point: the base oil's low-temperature flow limit, as a reference lower bound;
- Synthetic vs mineral: synthetic base oils far outperform mineral oil at low temperature.
Base oil low-temperature comparison
| Base oil | Minimum service temperature | Low-temp flow | Notes |
|---|---|---|---|
| Mineral oil | About −20°C | Poor | Thickens easily when cold |
| PAO synthetic | −40°C to −60°C | Good | Best value for low temperature |
| Ester oil | Below −60°C | Good | Common in aviation |
| Silicone oil | Below −70°C | Good | Poor steel-on-steel lubricity |
Common low-temperature scenarios
- Photovoltaic cleaners, smart valve actuators: −40°C micromotor bearings;
- Aviation / aerospace: −60°C general aviation grease;
- Cold chain and low-temperature storage equipment;
- Automotive electronics (cold winter starting).
Conclusion
Prioritize low-temperature starting torque and low-temperature penetration, then pour point. Below −40°C choose PAO or ester synthetic oil; below −60°C consider ester or silicone. Provide the minimum operating temperature and starting torque requirement for engineering confirmation.