The API maintains a system of Service Classifications (“S” ratings) for gasoline engines and Commercial Classifications (“C”ratings) for diesel engines. The procedures, and policies by which lubricants are rated is a constantly changing.Engines are getting smaller in sizes and output is getting higher and higher.Engine builders has to take care of fuel economy and stringent pollutions laws.This has led to an accreditation system and which involves representatives from the major automotive companies, API, oil manufacturers and government agencies which monitors and develop standards. Periodically changes are made to the specifications to keep up to date with current gasoline and diesel engine technology. Standards and tests are set by the American Petroleum Institute to ensure that appropriate engine oils perform in accordance with the requirements of vehicles currently in production.These requirements change as engines develop.Commercial vehicles are exposed to the most extreme driving conditions and as a consequence demand a lubricant to meet and exceed their requirements.They also operate in a business environment that demands the lowest operating costs possible.The broad range of commercial lubricants has been designed to meet both needs.
The Lubricant which delivers long-term performance, immediate protection from start up and helps to reduce vehicle pollutant emissions. The more efficiently the engine performs, the less fuel is consumed and pollution emitted which should be the main function of modern lubricant technology.
All the range of oils appropriately should meet or surpasses the stringent requirements developed by the Association of Constructors of European Automobiles (ACEA). This is the authorised trade association of the European vehicle manufacturers, and is essentially concerned with co-ordinating quality standards. The achievements of the ACEA standards for service-fill engine oils are a prime example of how the consumer benefits by being able to buy better quality products.
COMBINED API SERVICE CLASSIFICATIONS
Most motor oils are currently available in combined API Service Classifications. The combined classification is a high quality oil that is formulated with the proper base stocks and additive package to provide protection for both turbocharged gasoline and diesel powered engines in severe service applications. Combined API Service Classification motor oils are highly effective at reducing and controlling sludge and varnish deposits, acid and foam formation and have improved oxidation stability apart. An example of a combined API Service Classification is API CH-4/SJ etc.
API Diesel Engine Specifications are applicable and used widely now a days are CF-4,CG-4,CH-4,CI-4/CI-4+ and the latest one being CJ-4.