Skip the auto shop - Our mechanics make house calls
  1. Home
  2. Articles
  3. What Does API Stand for in Motor Oil?

What Does API Stand for in Motor Oil?

Motor Oil Types

The API designation in motor oil stands for the American Petroleum Institute. The API is the largest oil and gas industry trade organization. Among its many tasks, the API distributes more than 200,000 copies of its technical documents every year. These documents discuss the technical standards and requirements needed to achieve the standards.

API’s outreach covers not only the oil and gas industry, but also any industry that has an impact on the petroleum interests. Therefore, the API maintains such diverse categories as API standard on precision thread gauges, compression-ignited engines (diesel) and oil.

API’s oil classification system

Among API’s many standards is a system which ensures that oil provides uniform engine protection. Called the SN classification system and approved in 2010, it supersedes the older SM system. The SN system provides for:

• Better high-temperature piston protection • Improved oil sludging control • Improved compatibility for seals and oil aftertreatments (detergents)

To fully meet compliance with the SN standard, the oil must also provide better:

• Automotive emission systems protection • Automotive turbocharging system protection • Compliance with ethanol-based fuels

If an oil product meets all of these goals, it is considered to be SN-compliant and gains API approval. For consumers, it means that the oil is affordable, efficient, meets all applicable federal and state rules, protects the environment, and meets all safety standards. It is quite an aggressive agenda.

API seal of approval

When oil is approved as SN-compliant, it receives the equivalent of the API seal. Called the API donut, it looks like a donut as it identifies the standards that the oil meets. In the center of the donut, you find the SAE rating. In order to be approved for full compliance, the oil must be fully compliant with SAE oil viscosity standards. If an oil product is SAE (Society of Automotive Engineers) compliant, it receives the proper viscosity rating. Therefore, an oil that has been approved as an SAE 5W-30 oil will show that approval in the center of the API donut. The legend in the center will read SAE 10W-30.

You find the type of automotive product in the outer ring of the API donut. Indeed, that is the beauty of the API system. Using one mark of approval you find out more information. In this case, the outer ring of the API donut carries information about the type of vehicle and the model year of the vehicle.

The vehicle identifier is either an S or a C. The S means the product is made for a gasoline-powered car. The C means the product is made for a diesel-powered vehicle. This appears on the left-hand side of the two-letter identifier. On the right-hand side, you find the model year or model era designation. The current model designation is N. So, an oil product that has won API-compliance carries the identifier SN for a current gasoline-powered vehicle and CN for a current diesel-powered vehicle.

Please note that the new overall standard is called the SN standard. Designed in 2010, the new standard applies to vehicles made since 2010.

Importance of API compliance

Like SAE standard compliance, compliance with API standards gives consumers an extra level of confidence that an oil product meets a certain level of standardization. That standardization means that if a product is labeled 10W-30, then it meets the viscosity standards over a wide range of temperature conditions. Indeed, this oil will act like a 30-weight oil, providing this level of protection from about minus-35 to about 212-degrees. The API standard tells you whether the product is for a gasoline or a diesel engine. Finally, this standard tells you that the oil product is the same in New York, Los Angeles, Miami or Charlotte.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

How to Buy Fuel Treatments
Adding a fuel additive to your gas tank when you fill up is one way to clean vital engine parts of deposits, improve the performance of your engine,...
The Traveler’s Guide to Driving in Malaysia
CraigBurrows / Shutterstock.com Malaysia is a popular destination for many tourists today. The country has amazing sights and attractions that you will want to explore....
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...

Related questions

Q: Cylinder misfire and burning oil

The easiest way to diagnose the issue would be to have the vehicle scanned again. These codes will give you insight to things we would spend a lot of time testing for. If you are seeing smoke coming from the...

Q: Oil leaking in the bottom chassis. 2009 Chevrolet

Hello - there are 2 possibilities for an oil leak underneath the chassis as you describe. Engine oil, perhaps from the front crankshaft seal, or a timing cover leak, or a leaking power steering pump or hose. Power steering fluid...

Q: 2002 Infinity I35 oil leak/white smoke under hood

Valve cover gaskets are a common source of oil leaks. However since your engine has oil all over the block, it 's best to clean the engine of all the built up oil so the source of the leak can...