API OIL CLASSIFICATIONS FOR AMERICAN ENGINES
In this article we are going to talk about API, which is the equivalent of the ACEA for U.S. car manufacturers. These classifications emerged in 1947 at the initiative of the American Petroleum Institute (API), which has established several categories of oils since then, each of them defined by the type of service and by engine tests. The number of categories is not fixed, which means that the API can add additional categories where there is a need for new demands on manufacturers.
In the U.S., there are hardly any diesel cars or vans, they usually have gasoline engines. So when we speak of standards for diesel vehicles, we are referring to trucks, buses and public works machinery.
Deciphering the API code
To understand what these classifications mean, you have to bear two concepts in mind: lubricant application and service severity.
The first concept is indicated by the letter S if the oil is suitable for gasoline engines, and by the letter C if it is a lubricant for diesel engines. The second letter indicates the service severity that the oil can withstand.