1. Base Oil (70–90%)
This is the main component and serves as the lubricating medium. The type of base oil determines many of the grease’s properties.
- Types of base oils:
- Mineral oils (most common)
- Synthetic oils (e.g., PAO, esters, silicone oils)
- Vegetable oils (less common, used for biodegradable greases)
2. Thickener (5–15%)
The thickener gives the grease its semi-solid structure and helps it stay in place during operation.
- Types of thickeners:
- Soap-based thickeners:
- Lithium (most common)
- Calcium
- Aluminum
- Sodium
- Complex soaps (e.g., Lithium Complex, Calcium Complex)
- Non-soap thickeners:
- Polyurea
- Clay (bentonite)
- Silica
- Soap-based thickeners:
3. Additives (0–10%)
Additives enhance specific performance properties of the grease.
- Common additives include:
- Antioxidants: Prevent oxidation and extend grease life
- Corrosion inhibitors: Protect metal surfaces from rust
- Extreme Pressure (EP) additives: Improve load-carrying capacity (e.g., molybdenum disulfide, sulfur-phosphorus compounds)
- Anti-wear agents
- Tackifiers: Improve adhesion to surfaces
- Dyes or colorants for identification
Typical Example Composition (Lithium-based Grease):
Additives: 10%
Base Oil: 80%
Thickener (Lithium Soap): 10%