"High-temperature grease" is one of the most loosely used phrases in lubrication. Many products print an impressive dropping point on the tin, yet fail in a hot bearing within weeks. Choosing well starts with knowing what that number means and what it does not.
The dropping point is where grease turns liquid in a lab test, not a safe working temperature. For continuous high temperatures, choose by thickener: lithium complex for general hot duties, calcium sulphonate complex where heat combines with water or heavy loads, polyurea for long-life electric motor bearings, and synthetic or PFPE greases for extreme temperatures. Shorten relubrication intervals as temperature rises.
The dropping point (ASTM D2265) is the temperature at which a drop of grease falls from a heated test cup. It shows when the thickener structure gives way.
A grease stops working well long before that. Above about 70–80 °C, the base oil oxidises faster and bleeds out, and the grease hardens or turns to carbon. As a rough guide, the useful continuous limit of a grease is well below its dropping point, often by 80–100 °C or more, depending on base oil and additives. The maker's stated operating range is the better guide.
| Thickener | Typical dropping point | Strengths | Watch out |
|---|---|---|---|
| Lithium soap | about 180–200 °C | Cheap, versatile, good all-rounder | Struggles in continuous heat above about 120 °C |
| Lithium complex | 250 °C and above | Good heat and mechanical stability; the common hot-duty upgrade | Water resistance moderate |
| Calcium sulphonate complex | 300 °C and above | Excellent water resistance, natural EP and rust protection; heavy loads | Can be less pumpable in cold; check compatibility |
| Polyurea | about 240–260 °C | Long life, low noise; electric motors, sealed bearings | Often poorly compatible with lithium greases |
| Bentonite (clay) | No true melting point | Very high temperatures, intermittent heat | Base oil still oxidises; needs frequent relubrication |
| Synthetic base (PAO, ester) | Depends on thickener | Better oxidation life at high temperature | Price |
| PFPE (perfluoropolyether) | Very high | Extreme temperatures, chemical resistance | Very expensive; specialist use |
| Application | Usual choice |
|---|---|
| Electric motors, sealed and long-life bearings | Polyurea, or as the motor maker specifies |
| Fans, dryers, general hot bearings up to about 150 °C | Lithium complex |
| Steel mills, wet and hot, heavy loads | Calcium sulphonate complex |
| Kiln car wheels and oven conveyors | High-temperature synthetic or speciality grease |
| Bearings above about 180 °C continuously | Speciality synthetic or PFPE grease, per maker |
In ceramic plants, the kiln car wheels and roller kilns are classic hot points; see our guide for Morbi ceramic plants.
Heat consumes grease. A widely used bearing-maker rule halves the relubrication interval for every 15 °C rise above 70 °C. A bearing that needs greasing every three months at 70 °C may need it every six weeks at 85 °C and every three weeks at 100 °C. See how much grease a bearing needs.
Different thickeners can react when mixed: the mix may soften and run out, or harden. When switching to a high-temperature grease, purge the old grease thoroughly and monitor bearing temperature for the first days.
When you see these, check the actual temperature with an infrared thermometer before blaming the grease: a misaligned coupling or overgreasing can also cause heat. Read why overgreasing can damage bearings.
What is the best grease for high temperatures?It depends on the duty. Lithium complex suits most hot bearings, calcium sulphonate complex suits hot and wet heavy-duty points, polyurea suits long-life electric motors, and synthetic or PFPE greases suit extreme temperatures.
Can grease work at its dropping point?No. The dropping point is where the grease structure fails in a lab test. The safe continuous temperature is much lower.
Is high-temperature grease also water resistant?Not necessarily. Calcium sulphonate complex greases are known for water resistance; some lithium complex greases are only moderate. Check water washout results on the data sheet.
Can I mix polyurea and lithium grease?Often not. Polyurea and lithium greases are frequently incompatible. Purge the old grease before switching.
Tell us the bearing, its running temperature, speed and whether water is present, and our team will recommend the right high-temperature grease.