API’s development of engine oil standards is nothing new. We’ve been publishing them since the 1940’s. Normally, engine oil standards are developed to protect new and current engine technologies, meet government regulations, and ensure tests are in place to measure engine oil performance. All of these factors figured into the development of API CK-4 and FA-4. What’s different about the development is API’s introduction of two diesel engine oil standards at the same time. We haven’t done that since API CF and CF-2 in 1994.
https://www.api.org/products-and-services/engine-oil/eolcs-categories-and-classifications/latest-oil-categories
