API Service Classification for Passenger Car Engine Oil

API Service Classification for Passenger Car Engine Oil

API Service Classification

API Service Classification for Passenger Car Engine Oil

If you own a car, you might have encountered terms like API Service Classification on your engine oil containers. Have you ever wondered what these codes mean and why they are essential? Well, worry not! In this section, we’ll demystify API Service Classification for you, explaining the main differences between each classification. By the end, you’ll have a clear understanding of which engine oil is best suited for your beloved four-wheeler.

Understanding API Service Classification

API, or the American Petroleum Institute, has a system to classify engine oils based on performance levels and intended use. They use two letters (S for gasoline, C for diesel) followed by a number (like SAE 10W-30 or API SN).

Every new API classification caters to modern engine demands, considering factors such as design, emissions, fuel efficiency, and protection. As a car owner, using the right API Service Classification for your vehicle is crucial for optimal engine performance and longevity.

API Service Classification

Main Differences Between Each Classification

  1. API SA (Obsolete): introduced the first API classification. It provided minimal additive levels and was suitable for engines built before 1930. However, it lacks the necessary protection against corrosion, rust, and wear, making it unsuitable for modern engines. Therefore, oils with this classification are now scarce.
  2. API SB (Obsolete): followed API SA, providing slightly better performance in resisting oxidation and protecting against deposits. While it provided some improvements, it is still outdated and not suitable for modern vehicles. Similar to API SA, it is obsolete and rarely found today.
  3. API SC: The API SC classification brought improvements in engine protection compared to its predecessors. It was suitable for engines manufactured in the 1960s. API SC oils are not suitable for modern vehicles due to engine technology advancements and higher performance demands.
  4. API SD: API SD was an improvement over API SC, offering better detergency and anti-wear properties. It was intended for gasoline engines built in the 1970s. However, modern engines should not use it, considering it outdated like its predecessors.
  5. API SE: was an improvement over API SD, introduced to meet early 1980s engine requirements. While API SE was a step in the right direction, it is still outdated for contemporary engines.
  6. API SF: API SF brought further improvements to oil formulation, providing better control over sludge, piston deposits, and oil thickening. It was designed for late 1980s engines. Even though API SF oils are an improvement over their predecessors, modern engines consider them inadequate.
  7. API SG: The API SG classification saw significant progress in engine oil formulation, offering better engine protection and cleanliness. It was intended for use in engines from the early 1990s. However, API SG oils, while better, are now outdated and not recommended for use in newer engines.
  8. API SH: API SH was an upgrade over API SG, introducing improved oxidation stability and deposit control. It was formulated for late 1990s engines. API SH oils, like their predecessors, are no longer suitable for modern engines due to advancements in technology and performance requirements.
  9. API SJ: API SJ provided further advancements in engine oil performance, including better protection against sludge and deposit formation. It was intended for engines from the early 2000s. While API SJ oils were an improvement, they are now considered outdated for today’s car engines.
  10. API SL: API SL brought significant enhancements in engine oil formulation, providing better protection against wear, deposits, and oxidation. It was designed for engines in the mid-2000s. API SL oils are still commonly found, but they might not meet the requirements of the latest engine models.
  11. API SM: improved over API SL, controlling engine deposits and reducing oil consumption. It was intended for late 2000s engines and still provides good protection for older vehicles. Newer models may need a more advanced classification.
  12. API SN: API SN is the current specification for gasoline engines and represents a significant improvement over its predecessors. It offers better protection against low-speed pre-ignition (LSPI) and enhanced fuel economy. API SN oils are suitable for most modern vehicles, but always check your vehicle’s owner’s manual for the recommended oil specification.
  13. API SN Plus: is an improved version of API SN, meant to address Low-Speed Pre-Ignition (LSPI) in modern turbocharged gasoline direct-injection (TGDI) engines. LSPI is abnormal combustion causing engine knocking. It’s more common in downsized and turbocharged engines, but API SN Plus oils have additives to reduce LSPI, providing better protection. Using API SN Plus oil adds an extra layer of safeguard for your turbocharged vehicle, preventing potential LSPI-related engine problems.
  14. API SP: is the latest specification for gasoline engines, meeting the evolving needs of modern vehicles and complex engine designs. It improves upon API SN Plus, offering better protection and performance. It addresses the impact of ethanol-blended fuels, providing improved protection against deposits, wear, and oil oxidation. API SP oils meet LSPI prevention requirements, making them suitable for turbocharged engines. Using API SP oil is crucial if recommended by your vehicle’s manufacturer for optimal engine protection and performance.


Choosing the right engine oil for your car is vital to ensure its longevity and optimal performance. Understanding the differences between API Service Classifications can guide you in making the right decision. Always consult your car’s owner’s manual to find the recommended API classification for your specific vehicle. By using the right engine oil, you can keep your car running smoothly and enjoy many miles of trouble-free driving!

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