Base oils are the fundamental component of many lubricants and play a crucial role in ensuring the smooth performance of engines and industrial machinery. These oils are derived either from the refining of crude oil (mineral base oil) or produced through advanced chemical synthesis processes. Based on their composition, viscosity, sulfur content, and level of purity, base oils are categorized into five main groups — Group 1, Group 2, Group 3, Group 4, and Group 5. Each group offers distinct characteristics and performance advantages, making them suitable for various automotive, industrial, and specialty applications. Their quality and classification are essential in determining the efficiency, durability, and environmental impact of the final lubricant products.