Base oil, also known as base stock or base lubricant, is a refined petroleum product that plays a key role in the production of various lubricants, including motor oils, industrial oils, and greases. As the primary fluid medium, base oil carries essential additives and provides the lubrication necessary for the smooth operation of machinery and equipment.

Derived from crude oil, base oils undergo a refining process that removes impurities and enhances key properties such as viscosity, stability, and lubricating ability. This process includes distillation, solvent extraction, and other purification techniques, ensuring the high-quality characteristics needed for diverse industrial and automotive applications.

Base oils are classified into different groups based on their chemical composition, viscosity index, and performance characteristics. These classifications include:

Group I: Conventional mineral oils

Group II: Hydrocracked mineral oils

Group III: Highly refined mineral oils

Group IV: Synthetic oils (PAOs)

Group V: Specialty oils (esters, silicones, etc.)