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Base Oils

As the demand increases for high-performance lubricants, the use of higher-quality base oils becomes important. The American Petroleum Institute (API) classifies base oils using the following characteristics:

  • Viscosity Index
  • Saturate Level
  • Sulfur Content

Base oils can have a direct effect on the quality of finished lubricants, which makes them an important component in all lubricant formulations.

The five API categories for base oils are:

  • Group I: Viscosity index between 80 and 120, and less than 90% saturates and/or more than 0.03% sulfur.
  • Group II: Viscosity index between 80 and 120, and 90% saturates or greater and 0.03% sulfur or less.
  • Group III: Viscosity index of 120 or higher, and 90% saturates or greater and 0.03% sulfur or less.
  • Group IV: All polyalphaolefins (PAOs).
  • Group V: All other base stocks not included in Groups I through IV.

For more information, please contact our Technical Services department.