SINCE LUBRICANTS TYPICALLY CONTAIN OVER 80 % BASE OIL BY VOLUME, the physical and chemical properties of base oil play a key role in defining the ultimate performance profile of a lubricant and the additive technology that must be employed in formulation. As a result, the development of lubricants for transportation and industrial applications requires a thorough understanding of the chemical composition of base oil and how this influences other properties such as viscosity, viscosity index, and long-term thermal and oxidative stability.