What You Need to Know – Part 4

How Is Gasoline Engine Oil Classified?

Engine oils are classified according to performance standards designed to ensure that they meet the lubrication, protection, and operating requirements of modern engines.

The American Petroleum Institute (API) has developed a classification system for engine oils used in gasoline and diesel engines. These classifications help vehicle manufacturers, technicians, and consumers identify oils that meet specific engine performance requirements.

For gasoline engines, the API S-Series is commonly used to identify service categories for passenger vehicles.

API S-Series Service Classification

The API S-Series classification focuses on engine oils designed for gasoline-powered passenger vehicles.

API service categories are developed around important engine protection and performance requirements, including:

• Piston deposit control

• Oxidation resistance

• Sludge and varnish control

• Turbocharger protection

• Emission-control system compatibility

• Fuel economy

• Protection against abnormal combustion

• Compatibility with modern engine technologies

As engine technology develops, new API service categories may be introduced to address new performance requirements and emerging engine-related concerns.

API SN and SN Plus

API SN was introduced in October 2010 to provide improved protection and performance for modern gasoline engines.

API SN requirements included improvements in:

• High-temperature piston deposit protection

• Sludge control

• Seal compatibility

• Oxidation performance

• Emission-control system compatibility

• Turbocharger protection

• Fuel economy when combined with the applicable Resource Conserving requirements

• Protection for engines operating with ethanol-containing fuels up to E85

In 2017, API SN Plus was introduced as a supplemental category in response to concerns about Low-Speed Pre-Ignition (LSPI) in certain modern turbocharged gasoline engines.

The supplemental requirements added specific testing intended to help evaluate and improve protection against LSPI.

How API Classifications Develop

API gasoline engine oil classifications generally progress alphabetically as performance requirements become more demanding.

New classifications may be introduced when:

• New engine technologies require additional protection.

• Manufacturers identify new engine-related concerns.

• Environmental and emissions requirements change.

• Fuel economy requirements become more demanding.

• Additional testing is required to evaluate modern engine performance.

Newer API categories are generally designed to provide performance equal to or greater than earlier categories. However, backward compatibility should always be confirmed against the vehicle manufacturer’s requirements rather than assumed solely from the API category.

API Testing and Licensing

Before an engine oil can be licensed by API and use applicable API marks, it must meet the required performance specifications and testing requirements.

Testing may include laboratory and engine performance tests designed to evaluate properties such as:

• Wear protection

• Deposit control

• Oxidation stability

• Sludge control

• Piston cleanliness

• Turbocharger protection

• Fuel economy

• Emission-system compatibility

• Protection against abnormal combustion

API licensing helps provide a recognized system for identifying oils that meet established industry performance requirements.

What Is ILSAC?

ILSAC, or the International Lubricant Specification Advisory Council, is an organization involving automobile manufacturers from the United States and Japan.

ILSAC develops performance specifications for gasoline engine oils with a focus on areas such as:

• Engine protection

• Fuel economy

• Emissions-system compatibility

• Turbocharger protection

• Deposit control

• Oil-life performance

• Compatibility with modern fuels and engine technologies

ILSAC specifications are closely related to API gasoline engine oil categories because the specifications are developed around the requirements of modern vehicle manufacturers.

ILSAC GF-5

ILSAC GF-5 was introduced in October 2010 and established performance requirements for gasoline engine oils used in a wide range of passenger vehicles.

The specification focuses on:

• Improved high-temperature piston deposit protection

• Turbocharger protection

• Improved sludge control

• Improved fuel economy

• Emission-control system compatibility

• Seal compatibility

• Protection for engines operating with ethanol-containing fuels up to E85

ILSAC specifications are periodically updated as engine technology and vehicle requirements evolve.

API and ILSAC Specifications

API and ILSAC classifications are closely connected, but they are not exactly the same system.

API provides service categories and licensing requirements for engine oils, while ILSAC develops specifications focused primarily on gasoline engine oil performance requirements established by participating automobile manufacturers.

Many gasoline engine oils carry both API and ILSAC performance designations when they meet the applicable requirements.

When selecting an engine oil, always check the vehicle manufacturer’s recommended specification rather than relying only on the oil’s viscosity grade.

Resource Conserving

Resource Conserving is an API supplemental designation introduced in 2010 for certain gasoline engine oils.

It replaced the earlier Energy Conserving designation and expanded the performance requirements beyond fuel economy alone.

Resource Conserving requirements are associated with performance areas such as:

• Fuel economy

• Emission-control system protection

• Turbocharger protection

• Engine cleanliness

• Compatibility with ethanol-containing fuels

• Overall engine protection

The purpose of Resource Conserving oils is to help balance fuel-efficiency performance with the protection requirements of modern gasoline engines.

Why Engine Oil Standards Matter

Engine oil standards provide an important reference when selecting lubricants for modern vehicles.

Using an oil that meets the required API, ILSAC, or manufacturer-specific specification can help provide:

• Appropriate engine protection

• Improved deposit control

• Reliable lubrication

• Compatibility with emission-control systems

• Protection of turbocharged engines where required

• Support for fuel-efficiency requirements

• Compatibility with specified fuel types

However, not every engine oil on the market meets every industry specification. Consumers should therefore verify that the product carries the appropriate performance claims and certifications required for their vehicle.

Choosing the Right Gasoline Engine Oil

When selecting engine oil for a gasoline-powered vehicle, consider:

• SAE Viscosity Grade – Select the viscosity recommended by the vehicle manufacturer.

• API Service Category – Confirm that the oil meets the required API performance category.

• ILSAC Specification – Where applicable, verify the required ILSAC specification.

• Manufacturer Approvals – Check for any specific vehicle manufacturer approvals or requirements.

• Engine Technology – Consider whether the engine is turbocharged, direct-injection, hybrid, or uses other modern technologies.

• Operating Conditions – Consider climate, driving patterns, vehicle load, and service conditions.

Ignitol Gasoline Engine Oils

Ignitol Gasoline Engine Oils are formulated to provide reliable lubrication, engine cleanliness, wear protection, and consistent performance for gasoline-powered vehicles.

Selecting the correct Ignitol engine oil according to the recommended SAE viscosity grade, API category, ILSAC specification, and vehicle manufacturer’s requirements can help support reliable engine operation and long-term engine protection.

To Conclude

API and ILSAC classifications provide important performance guidelines for gasoline engine oils. As engine technology continues to evolve, lubrication requirements also become more demanding.

Understanding specifications such as API SN, API SN Plus, ILSAC GF-5, and Resource Conserving can help vehicle owners make more informed decisions when selecting engine oil.

Always refer to the vehicle manufacturer’s owner’s manual or official service information to determine the correct viscosity grade and performance specification for your engine.