Launched in 2006, American Petroleum Institute. The primary oil and natural gas trade association in the United States. API operates a voluntary licensing and certification program that allows engine oil marketers to use the API Engine Oil Quality Marks if their products meet specific requirements. CJ-4 the previous category for engine oil performance, was designed to meet the needs of exhaust emission after treatment technologies, while enhancing engine durability. API CK-4 and FA-4 continues to address those issues while introducing improved performance and an increased fuel economy component. The EMA requested that API CK-4 and FA-4 define improvements in A reaction occurring when oxygen attacks petroleum fluids. Oxidation is accelerated by heat, light, metal catalysts, and the presence of water, acids, or solid contaminants. Oxidation leads to increased viscosity and deposit formation. stability, shear stability and resistance to aeration.
Better fuel economy requires the use of lower High Temperature High Shear. A measure of a fluid’s resistance to flow under conditions resembling highly-loaded journal bearings in fired internal combustion engines, typically 1 million s–1 at 150°C. (high temperature high shear) A measure of a fluid's resistance to flow. A fluid with a higher viscosity flows less easily., fuel efficient engine oils. Today, the U.S. market is dominated by SAE 15W-40 lubricants for diesel engines, but it is likely that, with the advent of API CK-4 and FA-4, we will see an increased use of SAE 10W-30 oils. In response to the range of viscosity grades in the market, for the first time in history, the heavy-duty engine category is split into two: API FA-4 oils will be suitable for both existing and new engines as defined by the respective OEM and API CK-4 offers backward compatibility in higher HTHS viscosity grades.