What does the API rating indicate?

The API rating indicates the coding for specific engine use based on fuel type. The American Petroleum Institute (API) provides a standardized way to classify motor oils based on their performance and suitability for various types of engines. The rating system helps to ensure that oil meets the requirements for different engine designs and performance levels, particularly in relation to fuel types—such as gasoline or diesel—and their specific requirements. This ensures that engine components receive adequate protection under varying operational conditions.

In contrast, fuel efficiency for different vehicles does not pertain to the API rating, which focuses on oil specifications rather than vehicle performance metrics. General engine performance expectations can be informed by the API rating, but it is specific to oil and its compatible engine types rather than a broad performance descriptor. Weight and thickness of oil, often referred to as viscosity, is important for understanding oil characteristics but is separate from what the API rating signifies. Thus, the correct understanding of the API rating is its role in identifying suitable oil for specific engine types based on their operational needs and fuel types.