API is an abbreviation of the American Petroleum Institute – this is where the API system was created back in 1947.
There are 3 main types of API classification:
- For powertrain parts.
- For gasoline engines.
- For engines that run on diesel fuel.
API Engine Oil Grade
Meaning of letters
Engine oil standards by API are indicated by a two-letter marking:
- 1st letter: engine type designation – S – gasoline engine, C – diesel engine.
- 2nd letter: quality standard – the further the letter is from the beginning of the alphabet, the higher the quality. The modern standard for gasoline engines is L, for diesel engines it is F.
- Oils of the latest generation can also have a double slash, for example, API SG/CE – it means it is designed for both gasoline and diesel engines.