What Is API Oil Rating? SN, SP, SP-Plus Explained What Is API Oil Rating? SN, SP, SP-Plus Explained

Gasoline engine-oil quality guide

How to Read API SN, SN PLUS, SP and SQ Oil Ratings

An API oil rating is a performance category—not an oil viscosity. It tells you which gasoline-engine protection standard an oil has been tested and licensed to meet.

API SN is an older gasoline category, SN PLUS added extra low-speed pre-ignition protection, API SP introduced broader modern-engine protection, and API SQ became the newer gasoline category in 2025.

API SN Older gasoline-engine performance category

SN PLUS SN plus added LSPI protection

API SP 2020 category for modern gasoline engines

Current newer category API SQ, first licensed in 2025

Understand SP-Plus Compare the ratings Choose the right oil

Find the required API category Read the owner’s manual for SN, SP, SQ or another gasoline-engine service category.

Match the viscosity separately An API SQ 5W-30 oil does not replace required API SQ 0W-20 merely because both carry SQ.

Check manufacturer approval European and performance vehicles may require an OEM approval beyond the API rating.

Important terminology correction

Is API SP-Plus a Real Oil Rating?

The official name is SN PLUS—not SP-Plus

API created the SN PLUS classification before API SP. SN PLUS was designed to add low-speed pre-ignition protection to API SN oils used in turbocharged, direct-injection gasoline engines.

“API SP-Plus” is not the name of a separate gasoline-engine service category. People often use that phrase when they actually mean API SN PLUS, API SP, or a bottle that shows SP together with an SN PLUS-related claim.

What you may see on a bottle: API’s licensing rules can permit SN PLUS wording with certain licensed SN or SP products. That still does not create a stand-alone service category called “API SP PLUS.”

Current-category update: API SP is no longer the newest gasoline category. API SQ became available for licensed oils on March 31, 2025. A modern bottle may therefore show API SQ rather than SP.

The easy definition

What Does an API Oil Rating Tell You?

The American Petroleum Institute’s Engine Oil Licensing and Certification System defines performance categories and quality marks for licensed engine oils.

For passenger-car gasoline engines, the category begins with the letter S. The second letter moves through the category sequence as new standards are introduced.

Performance category

Examples: SN, SP and SQ

This identifies the gasoline-engine performance standard the oil meets.

Viscosity grade

Examples: 0W-20 and 5W-30

This describes the oil’s low-temperature and high-temperature viscosity classification.

Manufacturer approval

Examples: OEM-specific standards

This confirms whether the oil meets requirements established by a particular vehicle manufacturer.

These three items are not interchangeable. A bottle can carry the newest API category but still be wrong because its viscosity or manufacturer approval does not match your engine.

A practical example

Suppose your owner’s manual requires:

SAE 0W-20 viscosity
API SP or newer
ILSAC certification
A specific manufacturer specification

An API SQ 5W-30 oil satisfies the “SP or newer” part, but it may still be wrong because the viscosity is 5W-30 instead of 0W-20.

Category timeline and purpose

API SN vs SN PLUS vs SP vs SQ

API designation	Introduction	Main purpose	Practical buying meaning
API SN	2011 gasoline-engine service category	Improved high-temperature deposit protection, sludge control and seal compatibility compared with earlier categories	Suitable where the vehicle specifically calls for SN, provided viscosity and other specifications match
API SN PLUS	First licensed May 1, 2018	API SN performance with additional protection against low-speed pre-ignition in turbocharged direct-injection gasoline engines	Useful transitional category for engines vulnerable to LSPI before API SP became available
API SP	First licensed May 1, 2020	Protection against LSPI, timing-chain wear, high-temperature deposits, sludge and varnish	Can generally be used where SN and earlier gasoline categories were recommended
API SQ	First licensed March 31, 2025	Newer gasoline-engine category aligned with updated passenger-car oil requirements	Can be used where SP and earlier gasoline S categories were recommended, while still matching viscosity and OEM requirements

Fast buying rule

If your manual requires API SN, a correctly licensed API SP or SQ oil can normally provide the required gasoline-category performance.

If your manual requires API SP, choose API SP or API SQ—not an older SN-only oil—unless the vehicle manufacturer gives different instructions.

If your manual requires API SQ, use SQ. An older SP bottle should not automatically be treated as equivalent.

USE THE
REQUIRED
CATEGORY
OR NEWER

Older but still important

What Is API SN Oil?

API SN is a gasoline-engine service category associated with vehicles from the period before API SP was introduced. It improved several performance areas compared with earlier API categories.

API SN was designed to address

High-temperature piston deposits
Engine sludge and varnish
Seal compatibility
General gasoline-engine wear protection
Emissions-system compatibility when the correct formulation is used

API SN does not tell you

The correct viscosity for your vehicle
The engine’s oil capacity
Whether the oil is full synthetic
Whether it carries a required European OEM approval
How long the oil can remain in your engine

Should you still buy SN? If SP or SQ oil is available in the correct viscosity and specifications, the newer gasoline category is normally the more practical choice for an engine that originally required SN.

The real “Plus” classification

What Is API SN PLUS?

SN PLUS was an additional classification used with API SN. It addressed a modern gasoline-engine problem called low-speed pre-ignition, commonly shortened to LSPI.

LSPI risk

What low-speed pre-ignition means

LSPI is an abnormal combustion event that can occur in some turbocharged, gasoline direct-injection engines at low speed and high load.

A severe event can create very high cylinder pressure and may damage pistons, rings or connecting components.

SN PLUS purpose

Why the classification was added

SN PLUS required oils to provide additional LSPI protection while retaining the API SN performance level.

It served as an important step between API SN and the later API SP category.

SN PLUS is not the same as an additive package you pour into the engine. It is a licensed oil-performance classification achieved by the complete finished lubricant.

Modern gasoline-engine protection

What Is API SP Oil?

API SP was introduced for oils available from May 2020. It incorporated protection needed by newer gasoline engines while remaining suitable for many older engines that called for earlier API S categories.

LSPI

Pre-ignition protection

API SP includes protection against low-speed pre-ignition in applicable modern gasoline engines.

Timing chain

Chain-wear control

The category includes a timing-chain wear performance requirement important for many modern engine designs.

High temperature

Piston and turbo deposits

API SP strengthens protection against deposits formed under demanding high-temperature operation.

Cleanliness

Sludge and varnish control

The oil must satisfy requirements intended to keep internal engine surfaces cleaner.

Fuel economy

Resource Conserving option

Some API SP oils also qualify for Resource Conserving and related ILSAC requirements.

Older engines

Backward compatibility

API SP can generally be used where API SN and earlier gasoline S categories were recommended.

API SP is still a valid category. The existence of API SQ does not make every SP oil unsafe or unusable. Use the category required by the vehicle manufacturer.

Current newer category

What Is API SQ Oil?

API SQ is the newer gasoline-engine service category added for oils available in 2025. API’s current licensing standard permits SQ to appear in the upper portion of the API Service Symbol.

API SQ can replace earlier gasoline categories

API states that oils meeting SQ may be used where SP and earlier API S categories were recommended.

API SQ works with newer ILSAC standards

ILSAC GF-7A and GF-7B became effective on March 31, 2025 and provide the current basis for API passenger-car certification marks.

Backward-compatible category does not mean universal oil. API SQ 0W-16 is not suitable for an engine requiring 5W-40 merely because SQ is newer.

When choosing between SP and SQ: Buy SQ when it meets every specification and is reasonably available. SP remains acceptable when the manual requires SP and the product carries the correct viscosity and approvals.

Read the back label

How to Read the API Service Symbol “Donut”

API SERVICE SQ

5W-30

RESOURCE CONSERVING

Top of the Donut The API service category, such as SN, SP or SQ.

Centre of the Donut The SAE viscosity grade, such as 0W-20 or 5W-30.

Bottom of the Donut An optional classification such as Resource Conserving or SN PLUS where applicable.

Read the top first. Confirm the API gasoline category meets or exceeds the category required by the owner’s manual.

Read the centre separately. Confirm the SAE viscosity matches the exact engine and climate instructions.

Inspect the lower section. Look for Resource Conserving or other permitted supplementary wording when your vehicle requires it.

Check the rest of the bottle. Look for ILSAC certification, ACEA sequences and manufacturer approvals.

Confirm the product is API licensed. Use the official API licensee directory when a brand or label looks unfamiliar.

Donut, Starburst and Shield

What Is the Difference Between API Quality Marks?

API Donut

Shows category and viscosity

The Donut displays the service category in the upper section and the SAE viscosity in the centre.

API Starburst

Passenger-car gasoline certification

The Starburst identifies licensed oils meeting the current applicable ILSAC passenger-car requirements for eligible viscosity grades.

API Shield

Very-low-viscosity gasoline oils

The Shield is used for licensed oils meeting the applicable ILSAC requirement for SAE 0W-16 oils.

Current ILSAC link: As of March 31, 2025, GF-7A provides the current basis for the Starburst and GF-7B provides the basis for the Shield.

Do not use the Shield as permission to install 0W-16 in any vehicle. It only confirms certification. Your engine must also be designed and approved for that viscosity.

Can newer oil replace older oil?

Are API Oil Ratings Backward Compatible?

For automotive gasoline engines, newer API S categories generally include the performance properties of earlier categories.

Manual requires API SN API SP or API SQ can generally be used when viscosity and all other specifications match.

Manual requires SN PLUS API SP or SQ is normally the practical modern replacement because newer categories include LSPI-related performance requirements.

Manual requires API SP Use API SP or API SQ. Do not step backward to an SN-only oil unless the manufacturer permits it.

Manual requires API SQ Use SQ. An older SP oil should not automatically be substituted simply because the viscosity matches.

Classic or specialty engine Check specific requirements for catalyst compatibility, flat-tappet camshafts, phosphorus limits, racing use or historic specifications.

Gasoline backward compatibility does not automatically apply to diesel categories. Some diesel classifications, especially low-viscosity F categories, are not interchangeable with traditional C-category oils.

Practical buying process

How to Choose the Correct API-Rated Oil

Identify the exact engine. Use the model year, make, model, engine displacement, fuel type and engine code. Different engines in the same vehicle may require different oil.

Find the manufacturer’s required viscosity. Write down the full SAE grade, such as 0W-20, 5W-30 or 0W-40.

Find the minimum API category. Look for wording such as API SN, API SP, API SQ or “API SP or later.”

Check the ILSAC requirement. Many North American and Asian passenger vehicles also specify an ILSAC standard.

Check ACEA and OEM approvals. European vehicles may require an ACEA category plus a manufacturer approval that API alone cannot replace.

Inspect the bottle marks. Confirm the category, viscosity, certification marks and exact product approval wording.

Verify an unfamiliar brand. Search the API directory by company, brand, viscosity and service category.

Record what you installed. Save the oil brand, product name, viscosity, API category, quantity, filter and service date.

Best shelf-shopping rule: First eliminate every oil with the wrong viscosity or missing approval. Then compare API category, formulation, price and brand.

Do not confuse the specifications

API Rating vs SAE, ILSAC, ACEA and OEM Approval

Mark or standard	What it tells you	Example	Can it replace the others?
API	Gasoline or diesel engine-oil performance category	API SQ	No
SAE	Oil viscosity grade	SAE 5W-30	No
ILSAC	Passenger-car performance and efficiency requirements	ILSAC GF-7A	No
ACEA	European engine-oil performance sequence	ACEA C3	No
OEM approval	Vehicle-manufacturer-specific performance requirement	A manufacturer’s formal approval number	No

An API SQ label alone does not prove suitability for every European vehicle. The oil may still lack the required ACEA class or manufacturer approval.

Avoid misleading oil labels

How to Tell Whether an API Claim Is Trustworthy

Signs of a properly presented product

API Donut is clear and legible.
Viscosity matches the front and back label.
Brand and product appear in the API directory.
Container has a traceable batch or production code.
Tamper seal and cap are intact.
Manufacturer provides a technical data sheet.

Warning signs

Wording such as “API quality” without a clear licensed category
Misspelled API marks or distorted logos
Different viscosity printed in different places
No product traceability or company contact information
Price far below normal market pricing
Seller refilled or resealed container

“Meets API requirements” and “API licensed” are not always the same claim. Use the official directory when you specifically want confirmation that API licenses the product and its displayed quality marks.

Before buying an unfamiliar oil: Search the company, brand, viscosity and service category in API’s official licensed-oil directory.

Search the official API licensed-oil directory

International vehicle owners

Does API Rating Apply Outside the United States?

API categories appear on oils sold throughout many international markets. However, the vehicle manufacturer may prioritize different specifications depending on the country and engine.

Common North American and Asian pattern

SAE viscosity
API gasoline category
ILSAC standard
Manufacturer-specific requirement when applicable

Common European pattern

SAE viscosity
ACEA sequence
Formal OEM approval
API category as an additional specification on some products

Do not copy a US-market oil recommendation for a diesel, hybrid or European-market version. Engines, emissions systems and service specifications can differ by country.

Common API-rating mistakes

Mistakes to Avoid When Reading an Oil Bottle

Thinking SN means synthetic

The S identifies a gasoline-engine service category. It does not mean synthetic oil.

Thinking SP is a viscosity

SP is a performance category. Viscosity is shown separately as 0W-20, 5W-30 or another SAE grade.

Searching for SP-Plus

The official “Plus” terminology is SN PLUS. Newer gasoline categories are API SP and API SQ.

Buying the newest category in the wrong grade

API SQ 5W-30 can still be wrong for an engine requiring 0W-20.

Ignoring an OEM approval

Some engines require manufacturer testing beyond the API category.

Assuming API rating sets the oil-change interval

The vehicle manufacturer’s mileage, kilometre, time or oil-life-monitor schedule controls the interval.

Using gasoline oil in a diesel engine

Diesel engines use API C or F categories and may have strict after-treatment requirements.

Trusting the front label only

The front may emphasize marketing. Read the technical specifications and quality marks on the back.

API oil-rating FAQs

Frequently Asked Questions

What is an API oil rating?

An API oil rating is a licensed engine-oil performance category established through the American Petroleum Institute’s Engine Oil Licensing and Certification System. For gasoline passenger vehicles, examples include API SN, SP and SQ.

Is API SP better than API SN?

API SP is a newer gasoline-engine category and adds requirements for areas including low-speed pre-ignition, timing-chain wear and high-temperature deposits. It can generally be used where API SN was recommended, provided viscosity and other specifications match.

Is API SP-Plus an official category?

No stand-alone gasoline service category is officially named API SP-Plus. The official Plus classification is SN PLUS. People may also confuse this with API SP or a label that shows SP together with SN PLUS wording.

What is API SN PLUS oil?

SN PLUS is API SN oil with additional protection against low-speed pre-ignition in turbocharged, direct-injection gasoline engines. API began licensing SN PLUS oils on May 1, 2018.

What is the newest API gasoline oil rating?

API SQ is the newer gasoline-engine service category in API’s current licensing standard. Licensed oils were permitted to display API SQ beginning March 31, 2025.

Can API SQ replace API SP?

API states that SQ oils may be used where SP and earlier gasoline-engine S categories were recommended. The oil must still match the required viscosity, ILSAC or ACEA category and manufacturer approval.

Can API SP replace API SN?

Yes, API SP can generally be used where API SN and earlier gasoline categories were recommended. Always retain the correct SAE viscosity and any vehicle-manufacturer approval.

Does API SQ mean the oil is full synthetic?

No. API SQ is a performance category, not a base-oil description. A product may be full synthetic, synthetic blend or another formulation while carrying the category if it meets licensing requirements.

Where is the API rating printed on an oil bottle?

It is commonly shown in the upper portion of the circular API Service Symbol, often called the Donut. The SAE viscosity appears in the centre, and optional classifications may appear in the lower section.

Is API rating enough to choose engine oil?

No. You must also match the SAE viscosity, gasoline or diesel application, ILSAC or ACEA requirement, manufacturer approval, oil capacity and service interval for the exact engine.

Official technical references

Sources Used for This API Oil Rating Guide

API categories, licensing requirements and quality marks can change. Verify current requirements before purchasing oil for a new vehicle or unfamiliar engine.

Last official-source review: July 24, 2026.

Independent information notice: EngineOiil-Capacity.com is an independent informational website and is not the American Petroleum Institute, a vehicle manufacturer, an oil producer or a repair facility. Oil requirements vary by engine, model year, country, emissions system and service bulletin. Always follow the owner’s manual for viscosity, API or ACEA category, manufacturer approval, capacity and oil-change interval.