The oil is one of the most important lubricants in the automobile industry. Besides the base oil, mixing various additives like detergents, Dispersants, anti-wear materials, anti-oxidants, etc., into the base oil is crucial to produce a lubricant with an appropriate operation for a specific automobile. Different levels of performance could be achieved according to the structure of these additives, their Dosage, and their compatibility with each other. Various institutions around the world classify the engine oils based on certain tests that simulate the operating conditions of the automobile engine. American Petroleum Institute (API) has classified the engine lubricants for both Gasoline  and diesel engines. The group that begins with the Latin letter “C” expresses the performance levels of diesel engines. The sequence of the next letters demonstrates the performance development, respectively.