What is the API SQ engine oil specification?
As passenger car engines continue to evolve towards smaller, more efficient and highly engineered designs, lubricant technology must also advance. The introduction of the API SQ engine oil category reflects the industry’s response to tighter fuel economy targets, reduced emissions requirements, and the increased demands placed on modern petrol engines.
What is API SQ?
API SQ is the latest petrol engine oil performance category introduced by the American Petroleum Institute (API). It builds upon the previous API SP specification, introducing more stringent testing and enhanced performance requirements.
The standard was developed through API’s established accreditation process, which evaluates lubricant performance, durability, safety and environmental impact. API SQ is designed specifically to support the needs of modern, high-efficiency passenger car engines.
Why the Industry Needed API SQ
Modern petrol engines are typically:
- Smaller and more highly stressed
- Turbocharged and direct-injected
- Designed to meet tighter emissions limits
- Optimised for improved fuel economy
These design trends increase the demands placed on engine oils. API SQ oils are formulated to address these challenges while maintaining backwards compatibility with earlier specifications where appropriate.
Key Performance Improvements in API SQ
Enhanced Fuel Economy
Reducing internal engine friction remains critical for improving efficiency. API SQ oils are formulated to support lower friction performance, helping manufacturers meet increasingly strict fuel economy targets.
Stronger LSPI Protection
Low-speed pre-ignition (LSPI) is a known risk in modern turbocharged petrol engines and can lead to severe engine damage. API SQ introduces strengthened requirements to help mitigate LSPI events and protect highly loaded engines.
Improved Engine Cleanliness
Deposit control remains a major focus. API SQ oils are designed to better manage sludge and deposits, helping maintain engine efficiency and long-term reliability.
Increased Wear Protection and Durability
The new category raises the bar for wear protection, including improved timing chain protection. This supports extended component life in today’s precision-engineered engines.
Emissions System Compatibility
API SQ maintains tight limits on sulphated ash (maximum 0.9%), helping protect gasoline particulate filters and catalytic systems from ash-related blockage and performance loss.
Updated Engine Test Requirements
One of the most significant advances in API SQ is the strengthening of the Sequence engine tests used to validate oil performance.
Key tests include:
- Sequence IIH – evaluates high-temperature viscosity increase and deposit formation
- Sequence VH – measures low-temperature sludge and deposit control
- Sequence VI – assesses fuel economy performance
API SQ oils must demonstrate improved performance across these updated test regimes compared with API SP.
Support for Ultra-Low Viscosity Oils
API SQ also prepares the market for the growing use of ultra-low viscosity grades, including 0W-8 and 0W-12, which are increasingly specified by OEMs pursuing maximum fuel efficiency.
While closely aligned with the latest ILSAC GF-7 standard, API SQ uniquely accommodates these emerging viscosity requirements.
Backwards Compatibility
In most applications, API SQ oils are designed to be backwards compatible with earlier API SP and ILSAC GF-6 requirements (always subject to OEM recommendations). This allows fleets and motorists to adopt the newer technology without widespread compatibility concerns.
What This Means for End Users
For vehicle owners and operators, API SQ oils deliver:
- Improved engine protection
- Enhanced cleanliness and durability
- Better support for modern emissions systems
- Potential fuel economy benefits
- Reduced long-term maintenance risk
As engine technology continues to advance, specifications such as API SQ ensure lubricant performance keeps pace with evolving OEM requirements. Rock Oil’s SYNTHESIS SPORT 5W-30 and SYNTHESIS SPORT 5W-40 are engineered to meet the performance intent of the latest API SQ category, supporting the demands of modern, high-efficiency petrol engines.
Further Information
For technical guidance on API SQ–compliant lubricants, or to discuss the most suitable product for your application, please contact the Rock Oil technical team.