High quality engine oil is formulated with the proper base stocks and additive package to provide protection for both gasoline and diesel powered engines in severe service applications.
Engine oil must meet standards that are set by API, ACEA, IS, OEM etc.
API is the American Petroleum Institutes standards for motor oil & ACEA is the European standards.
The API service classes have two general classifications: S for "Service" (orgininating from Spark ignition) (typical passenger cars and light trucks using gasoline engines), and C for "Commercial" (originating from Compression ignition) (typical diesel equipment).
The latest API service standard designation is SM for gasoline automobile and light-truck engines. The SM standard refers to a group of laboratory and engine tests, including the latest series for control of high-temperature deposits. Current API service categories include SM, SL and SJ for gasoline engines. There are seven diesel engine service designations which are current: CJ-4, CI-4 Plus, CI-4, CH-4, CG-4, CF-4, and CF.
It is possible for an oil to conform to both the gasoline and diesel standards.
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.