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What is API classification?

By 2020-03-22July 25th, 2021No Comments

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:

  1. For powertrain parts.
  2. For gasoline engines.
  3. 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.

api classifications


David Muench (Carnes Mechanical)

David Muench (Carnes Mechanical)

Hey, I’m David. I’ve worked in a cars store for 6 years. I write reviews and guides, helping people to choose the most suitable technicals and best product for them. I’m happy to finally share my knowledge of the industry here, on CarnesMechanical.

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