Dropping point ≠ operating temperature
This is the most common mistake in high-temperature selection. Dropping point is the physical test temperature where the grease starts to drip; operating temperature is the recommended long-term working range based on oxidation stability, base-oil evaporation and thickener structure — usually far below the dropping point. Always select by operating temperature.
Base oil by temperature range
| Range | Recommended base oil | Notes |
|---|---|---|
| 120°C–150°C | Mineral / semi-synthetic | Low cost, normal duty |
| 150°C–200°C | Fully synthetic PAO / ester | Good oxidation resistance, long life |
| 200°C+ | Perfluoropolyether (PFPE) / phenyl silicone | Extreme high temperature, higher cost |
Thickener choice
- Lithium / lithium complex: common, cost-effective;
- Polyurea: high temperature, long life, suitable for motor bearings;
- PTFE: high temperature and chemical resistance, used with PFPE for extreme duty.
Key evaluation criteria
- Evaporation loss: faster base-oil evaporation means the grease dries out sooner;
- Oxidation stability: determines coking and hardening speed at high temperature;
- Safety margin: operating temperature should be at least 30°C below dropping point.
Conclusion
Below 150°C, a good synthetic grease is sufficient; above 150°C, watch evaporation loss and oxidation stability; above 200°C, consider PFPE. Never judge by dropping point alone.