How to Choose the Right Grease Oil for Your Application
When selecting the right grease oil, operating temperature range is one of the most critical factors to consider. Grease oil is composed of base oil, thickener, and additives, and its temperature tolerance depends on the properties of all three components.
Manufacturers usually provide a minimum and maximum operating temperature for each grease oil. When choosing, you must match these limits with the lowest start-up temperature and highest operating temperature of the lubrication point.
1. Minimum Operating Temperature
As temperature drops, grease oil becomes harder and more viscous, making it difficult to reach lubrication points. This can lead to insufficient lubrication during cold starts.
The minimum operating temperature should be higher than the lowest ambient temperature at cold start.
In extremely low temperatures (e.g., around -30 °C), synthetic grease oils—especially those with PAO (Polyalphaolefin) base oils—are recommended for better fluidity.
2. Maximum Operating Temperature
Grease oil specifications include a dropping point, which is the temperature at which the grease oil begins to melt. However, the maximum operating temperature is usually 30 °C to 50 °C lower than the dropping point.
Prolonged operation above this limit accelerates oxidation, degrades performance, and can permanently damage the grease oil—even if it cools down later.
High-Temperature Performance Risks
• Oxidation & Acid Formation – Overheating accelerates chemical breakdown, producing acidic compounds that degrade thickeners.
• Oil Separation – Base oil leaks from the thickener, reducing lubrication ability.
• Local Hot Spots – May result from misaligned bearings, incorrect grease oil quantity, excessive load, vibration, or wrong product choice.
When temperatures regularly exceed 90 °C, premium grease oils with synthetic oils and high-performance thickeners (e.g., lithium complex, polyurea, calcium sulfonate complex) are recommended.
3. Understanding Base Oils and Viscosity Index
Since grease oil primarily lubricates via its base oil, the oil’s viscosity-temperature characteristics are important.
A higher Viscosity Index (VI) means the oil maintains stable viscosity over a wider temperature range.
Base oils are classified by the API into five groups, each with different performance levels. Knowing the base oil type in your grease oil helps ensure suitability for your operating environment.
4. Low-Temperature Performance
At low temperatures, grease oil hardens, reducing mobility. Like edible oils, it flows freely at room temperature but thickens when cold.
Two important low-temperature indicators are:
• Pour Point – The temperature at which the oil stops flowing. Mineral oils typically have pour points between -20 °C and -30 °C.
• Low-Temperature Torque – Resistance a grease oil provides to bearing rotation at low temperatures. Lower torque means easier startup and less power loss.
If the grease oil’s low-temperature starting torque is too high, it may lock the bearing and prevent operation.
Key Temperature-Related Specifications to Check
When selecting grease oil, make sure these parameters align with your operating conditions:
• Dropping Point
• Maximum Operating Temperature
• Minimum Operating Temperature
• Base Oil Pour Point
• Low-Temperature Torque
• Base Oil Viscosity Index
Final Recommendation
To ensure long-lasting equipment performance:
1. Match grease oil temperature range to the actual operating conditions.
2. Select base oil type and thickener according to required temperature resistance.
3. Use synthetic and high-performance grease oils for extreme temperatures.
Choosing the right grease oil is not just about cost—it’s about reliability, longevity, and protection of your machinery.
