Motor oils also have different classifications that mandate what age of engine it's best used in. According to the United States Department of Energy, this is also called the API (American ...

Service Classifications The API Service Classification is a two letter designation based on the oil's performance. Oils for use in gasoline engines have an "S" followed by a letter from "A" to "G".

API will introduce a special service symbol donut to help consumers identify FA-4 diesel engine oil. The new donut features a shaded section to differentiate API FA-4 diesel oils from CK-4 oils.

The 2024 FleetOwner Specs Guide offers detailed information on engine oils and more. These specs cover many lubricant types and include information on various brands, SAE grades, API service ...