When choosing oil for your vehicle, you should always look or ask for API-licensed oil. API has made it easy to find these oils: licensed oils display one or both of the API motor oil quality marks—the API Service Symbol "Donut" and the Certification Mark "Starburst." These marks are part of API's Engine Oil Licensing and Certification System (EOLCS), a voluntary licensing and certification program that authorizes engine oil marketers meeting API requirements to display the API quality marks.


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The API Service Symbol, also known as the “Donut”

1. Performance Level

Motor oils designed for cars, vans, and light trucks with gasoline engines fall under API’s “S” (Service) categories. Motor oils designed for heavy-duty trucks and vehicles with diesel engines fall under API’s “C” (Commercial) categories. Please see the Gasoline Engines and Diesel Engines charts on the next pages for descriptions of current and obsolete API service categories.

2. Viscosity Grade

The measure of an oil’s ability to flow at certain temperatures. Vehicle requirements may vary. Follow your vehicle manufacturer’s recommendations on SAE oil viscosity.

3. Resource Conserving and Energy Conserving

These designations apply to oils intended for gasoline-engine cars, vans, and light trucks. Widespread use of “Resource Conserving” or “Energy Conserving” oils may result in an overall savings of fuel in the vehicle fleet as a whole.

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The API Service Symbol, also known as the “Donut”

4. Multiple Performance Levels

Oils designed for diesel engine service might also meet gasoline engine service. For these oils the designation is “C” category first followed by the “S” category. “C” category oils have been formulated primarily for diesel engines and may not provide all of the performance requirements consistent with vehicle manufacturers’ recommendations for gasoline-fueled engines.

5. The API Service Symbol with CI-4 Plus

The “CI-4 PLUS” designation identifies oils formulated to provide a higher level of protection against soot-related viscosity increase and viscosity loss due to shear in diesel engines. When originally introduced, CI-4 PLUS identified CI-4 oils meeting a higher level of performance. CJ-4 oils include all CI-4 PLUS performance requirements. CI-4 PLUS appears in the lower portion of the API Service Symbol “Donut.”

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The API Certification Mark, also known as the “Starburst”

An oil displaying this mark meets the current engine protection standard and fuel economy requirements of the International Lubricant Specification Advisory Committee (ILSAC), a joint effort of U.S. and Japanese automobile manufacturers. Automobile manufacturers recommend oils that carry the API Certification Mark. See the ILSAC STANDARD FOR PASSENGER CAR ENGINE OILS chart below for descriptions of current and obsolete ILSAC standards.

API’s Certification Mark and Service Symbol

identify quality motor oils for gasoline and diesel-powered vehicles. Oils displaying these marks meet performance requirements set by U.S. and international vehicle and engine manufacturers and the lubricant industry. More than 500 companies worldwide participate in this voluntary program, which is backed by a marketplace sampling and testing program.

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