What Is the API SQ Engine Oil Specification?
Modern petrol engines ask a great deal of their oil. Turbocharging, direct injection and efforts to improve fuel efficiency place demanding requirements on lubricants, particularly when it comes to controlling wear, deposits and abnormal combustion.
API SQ is the latest petrol engine oil performance category from the American Petroleum Institute. It builds on API SP, helping lubricant performance keep pace with developments in engine technology.
For vehicle owners, the useful question is straightforward: what does SQ offer, and is it suitable for your engine?
What is API SQ?
API SQ defines performance requirements for petrol engine oils used in passenger cars, SUVs, vans and light-duty trucks. Licensing against the category began on 31st March 2025.
It covers areas including engine cleanliness, wear protection and resistance to oil deterioration. Qualifying oils can be licensed through API’s Engine Oil Licensing and Certification System.
An API SQ specification identifies a performance level. It does not, by itself, establish the correct viscosity or replace any additional approval required by the vehicle manufacturer.
Why did the industry need another specification?
Many modern petrol engines combine smaller displacement with turbocharging and direct injection to deliver power efficiently.
These designs can create particular lubrication challenges. Oils must protect highly loaded components, control deposits and support reliable operation while manufacturers pursue lower fuel consumption and emissions.
SQ develops the performance framework used for SP, including stronger protection against low-speed pre-ignition as oil ages.
Stronger protection against low-speed pre-ignition
Low-speed pre-ignition, usually shortened to LSPI, is abnormal combustion that occurs before the intended spark. It can affect some turbocharged, direct-injection petrol engines and may cause serious damage.
API SP already addressed LSPI using a fresh-oil test. SQ adds an aged-oil assessment, helping establish that protection remains effective after the lubricant has undergone controlled ageing.
This is a significant development because engine oil needs to perform throughout its service interval, rather than only when freshly filled.
Engine cleanliness and wear protection
Controlling deposits helps keep pistons, turbochargers and other components working effectively. Wear protection is equally important for parts such as the valvetrain and timing chain.
The SQ testing framework includes assessments such as:
- Sequence IIIH: high-temperature oxidation and piston deposits.
- Sequence VH: sludge and varnish control.
- Sequence IX: LSPI protection, including the aged-oil assessment.
- Sequence X: timing-chain wear.
The applicable requirements depend on the specification and viscosity grade. SQ should not be described as introducing a completely new test for every performance area.
What does SQ mean for fuel economy?
Fuel economy is particularly relevant to API SQ with Resource Conserving and the closely related ILSAC GF-7 standards.
Resource Conserving adds requirements beyond the basic SQ category. An SQ claim alone therefore does not establish that every oil has passed the same fuel-economy tests or meets an ILSAC specification.
For drivers, potential savings depend on the engine, operating conditions and lubricant being replaced. The correct oil must still provide the viscosity and performance required by the manufacturer.
Compatibility with emissions-control systems
Engine oils also need to suit the vehicle’s catalysts and particulate filters.
The SQ framework includes chemical limits that vary with the viscosity grade and whether Resource Conserving requirements are claimed. It is therefore inaccurate to describe a maximum sulphated ash content of 0.9% as a universal limit for every SQ oil.
Where a vehicle requires a particular ACEA category or manufacturer approval for its emissions equipment, check that requirement alongside API SQ.
Does API SQ cover ultra-low-viscosity oils?
Yes. SQ accommodates grades including SAE 0W-8 and 0W-12, alongside more familiar viscosities.
These grades serve engines specifically designed for them. Their inclusion does not mean an older engine should be switched to a thinner oil.
API SQ also has a broader viscosity scope than ILSAC GF-7, so the two specifications should not be treated as interchangeable.
Can SQ replace SP?
API SQ can service petrol engines calling for SP and earlier API S categories, provided the chosen oil also meets the vehicle’s required viscosity and additional specifications.
However, an SQ claim alone does not demonstrate replacement suitability for every oil carrying an ILSAC claim. Check the complete product specification.
Rock Oil SYNTHESIS SPORT and API SQ
Rock Oil lists API SQ among the performance specifications for both SYNTHESIS SPORT 5W-30 and SYNTHESIS SPORT 5W-40.
These advanced synthetic, reduced-ash oils provide options for suitable passenger-car and light-commercial applications. Each grade has its own specification profile, so selection should be based on the individual engine’s requirements.
Explore Rock Oil’s automotive lubricants and SYNTHESIS range, or contact our technical team for help choosing a suitable product.