Petroleum Quality Institute of America

The Petroleum Quality Institute of America (PQIA) is an independent resource for information and insights on the quality and performance of lubricants in the marketplace.  Our mission is to serve the consumer of lubricants by reporting on the quality and integrity of lubricants in the marketplace.  




  • Did you know that there are engine oils on the shelf that can harm your engine?

  • Did you know that  there are codes on the bottle that tell which oils protect and which could harm your engine?

  • Do you know where to find these codes?

  • The American Petroleum Institute (API) knows, as do the engine builders, and the oil companies.

Read on, and now you will know.

Truth be told, you (the consumer - the car owner) are the ones ultimately responsible for assuring that the engine oil used in your car is "right for your car." And "right for your car" means, the oil meets the specifications required by your car's manufacturer, as detailed in your owner's manual. Keep in mind, use of anything other than that can void your warranty.

With that said, what follows are guidelines to assist you in understanding and interpreting the codes/acronyms on a bottle of oil to assure you are using the "right stuff." For car owners that have their oil changed at fast lubes, new car dealers and others, what follows provides you with the knowledge you need to ask the right questions. For most, that question is, "Does the oil you are servicing my car with meet the API, ILSAC, and other specifications required for my engine, and is it the right viscosity grade for my car's make model and year?" If the ones changing your oil can't answer these questions, it's time to change the ones changing your oil.

What API Service Classification is Required for Your Engine?

The service rating of passenger car and commercial automotive motor oils is classified by the American Petroleum Institute (API). The API program certifies that an oil meets certain Original Equipment Manufacturer (OEM) quality and performance standards. The service rating is shown in the API "Service Symbol Donut" on the product label.

The labels include two important pieces of information to determine if an engine oil is appropriate for use in your vehicle. The first piece of information speaks to viscosity grade. The Society of Automotive Engineers (SAE) defines a numerical system for grading motor oils according to viscosity. The suffixes (0, 5, 10, 15 and 25) followed by the letter W designate the "winter" grade of an engine oil.

The second piece of important information on the label is the  API service classifications. The API service classification is a two-letter code starting with either an "S" for gasoline engines or a "C" for diesel engines. The second letter in the API service classification is very important as it effectively speaks to the model years the engine oil was formulated to serve. As an example, the first API service classification was "SA" and these oils were designed to meet the requirements of cars built prior to 1930. The API SA service classification was followed by SB, SC, SD, SE, SF, SG, SH, SJ, SL, SM and to its current level of API SN.

For more information on the API Service classification system, click here.


What ILSAC Rating is Required for Your Engine?

In addition to an API Service Classification, your owner's manual may also specify a International Standardization and Approval Committee (ILSAC) requirement such as GF-3, GF-4 and GF-5  ILSAC adds an extra requirement of fuel economy testing to its specifications.  ILSAC GF-5 is the latest ILSAC standard. This standard applies to SAE 0W-20, 5W-20, 0W-30, 5W-30, and 10W-30 viscosity grade oils.

For more information on ILSAC, click here

Now that you have a better understanding of how to read an engine oil label, what should you do next?

Step 1: Go to your owners manual to find which oil is required for your engine. This will usually reference an API specification such as SN, SM, SJ, etc, and such  ILSAC specifications as GF-3, GF-4, GF-5, and/or other specifications. Also look for the viscosity grade recommended for your engine (i.e. 5W-30, 5W-20, etc). You need to know this information - write it down. If you can't locate your owners manual, an excellent resource for information on where to go for an online version is

Step 2: Go to your favorite retail outlet with your list of engine oil specifications in hand and read the labels on the bottles. Make sure the oil you purchase meets the specifications in your owner's manual. If you do not find the proper specification "codes" on the bottle don't buy the oil. It's that simple.

Step 3: If you have the oil changed for you at a fast lube, new car dealer or other service center, bring your list of specifications with you and confirm that the oil they put in your car complies with the specifications required for your car.


The following are some examples of engine oil labels showing where the "codes" are located and what they mean.  It should be noted that, with the exception of California, there are no laws that prohibit the sale of  engine oils identified by the API as having an "obsolete" status.

PQIA is not commenting on the quality of the products shown below as examples or the integrity of the manufacturers, but rather,  is intending to educate you, the consumer, in understanding what is written on the oil label and selecting and/or requesting the appropriate engine oils for use in your vehicle.

It is also important to note that some lubricant manufactures offer a product line that includes engine oils that meet current specifications (i.e. API SM GF-4), and in addition, offer other engine oils that meet such obsolete specifications as API SA and SB.  It is up to the consumer to read the labels (and their owners manual) to make the right choices for their vehicles. 

Example of an SM label: Shell Formula 5W-30

Price: $2.99 a quart at an auto parts store in New Jersey - January 2010

Example of an SG label: XCEL XHD TURBO 5W-30

Price: $3.99 in New Jersey - January 2010





Price: $3.99 a quart at a C-store in December 2009



Note: In addition to API SB, Amalie also offers a full line of conventional and synthetic engine oils labeled as meeting the current API SM GF-4 specification. As previously noted, it is up to the consumer to read the labels (and their owners manual) to make the right choices for their vehicles. 

Example of SA label: PartsMaster SA 40 Motor Oil

Price: $2.89 a quart at an auto parts store in New Jersey - March 2010



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