Composition of lubricating greases

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

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%