KnowledgebasE Article

Understanding API in relation to automotive lubricants

The American Petroleum Institute (API) is a critical body in the automotive lubricant and oil industry. It assigns API ratings to automotive oil blends that meet the standards set by the International Lubricant Standardization and Approval Committee (ILSAC), a group managed by U.S. and Japanese automobile manufacturers.API ratings play a significant role in determining which automotive oil and lubricant is suitable for your engine.

What is an API Rating?

An API rating, signified by a seal of approval, assures that the oil has met the minimum performance standards of car manufacturers. API ratings typically follow these formats:

Two letters starting with ‘S’ (e.g., SN, SM): These oils are designed for petrol engines.

Two letters starting with ‘C’, followed by a ‘-4’ (e.g., CJ-4, CI-4): These oils are formulated for diesel engines.

API ratings change periodically to accommodate evolving engine parts and technology.

Why Do API Ratings Change?

As automotive parts manufacturers develop more advanced parts, the required automotive oil properties (viscosity, protection, compatibility) must also adapt. Whenever automotive oil is modified to match these advancements, its API rating is updated.

Automotive oils with outdated API ratings may not provide the necessary lubrication for newer engines, which can cause premature wear. Consequently, it’s crucial to choose automotive lubricants with the most recent API rating, especially for cars less than 15 years old.

Impact of Expired Oil

Motor oil degrades over time, even when unused. Expired oil can fail to adequately lubricate an engine, risking premature wear. Therefore, ensuring that the oil or lubricant you’re using is fresh is vital.

Compatibility with Older Engines

Fortunately, newer motor oil blends with recent API ratings are backwards compatible, meaning they work perfectly fine in older engines. However, automotive oils with older API ratings aren’t compatible with newer engines due to their inability to withstand the heat produced by these engines.

Current and Obsolete API Ratings

API ratings change over time, with some becoming obsolete. As of this writing, the current API ratings for petrol and diesel engines are:

Petrol Engines:

  • SN: For vehicles manufactured after 2010
  • SM: For vehicles manufactured between 2004 and 2009
  • SJ: For vehicles manufactured between 2001 and 2004

Diesel Engines:

  • CJ-4: For four-stroke high-speed diesels manufactured after 2010
  • CI-4: For vehicles manufactured between 2002 and 2010
  • CH-4: For vehicles manufactured between 1998 and 2002

Older ratings are considered obsolete and may not be suitable for modern engines. Always opt for automotive oils and lubricants with the most recent API rating for optimal engine performance and protection.

SN: The Latest API Rating for Petrol Engines

SN is the latest API rating for petrol engines. Compared to its predecessor, it offers several advantages, including:

  • Improved fuel economy
  • Enhanced life of emission system components
  • Better control over sludge, deposits, and oxidation
  • Superior low-temperature viscosity
  • Enhanced corrosion protection
  • Improved turbocharger protection
  • Better filter clogging protection
  • Superior seal compatibility

Understanding API Service Categories

The API Service Classification can be a helpful guide when choosing motor oil. It has evolved over time, starting from API SA (for vehicles built in the 1920s) and progressing to SB, SC, SD, etc. For example, if an oil only meets the API SA classification, it is suitable for use in vehicles manufactured in the 1920s. Current motor oil classifications range from SG to SN for petrol engines and CD to CJ for diesel engines.

Each classification signifies a distinct level of performance and compatibility with specific engines. For instance, SM classification was introduced in November 2004, improving oxidation resistance, deposit protection, and wear protection and delivering better low-temperature performance over its predecessors. It’s crucial to check these classifications when buying motor oil for your vehicle.

In Conclusion

The API rating on your automotive oil signifies its performance capabilities and compatibility with your vehicle’s engine. Ensure that the motor oil you choose meets or exceeds your vehicle’s manufacturer’s requirements to maintain optimal engine health and performance.