Service Classifications (in North America) are determined by the American Petroleum Institute (API), while oil viscosity grades are determined by the Society of Automotive Engineers (SAE). They are divided into two categories: "S" categories and "C" categories. The "S" (Service/Spark ignition) classifications are for oils designed for gasoline engines; the "C" (Commercial/Compression Ignition) classifications are for oils designed for diesel engines or commercial vehicles.
"API's Engine Oil Licensing and Certification System (EOLCS) is a voluntary licensing and certification program that authorizes engine oil marketers who meet specified requirements to use the API Engine Oil Quality Marks—the API Service Symbol "Donut" and Certification Mark "Starburst". [api.org]
In other words, the Licensee pays a Licensing Fee to API which then entitles them to use the coveted API Service Symbol "Donut" on the back label of their Motor Oil as well as the API Certification Mark, also known as the "Starburst" on the front label.
An API license indicates that a specific motor oil formulation has passed the minimum performance standards as defined by a series of laboratory bench, physical, chemical and engine tests. While the Licensed Motor Oil must meet the established minimum for performance under a specified API Category, other than this minimum performance requirement, there is no differentiation in any product that exceeds the minimum.
The latest API spec for gasoline vehicles is SN PLUS (SP should be coming out in the next year or two).
ILSAC stands for International Lubricants Standardization and Approval Committee. It was formed in 1992 by AAMA (American Automobile Manufacturers Association - representatives of DaimlerChrysler Corporation, Ford Motor Company and General Motors Corporation) and JAMA (Japan Automobile Manufacturers Association) to define the need, parameters, licensing and administration of lubricant specifications.
Together with the Tripartite system (API, SAE and ASTM) they formed EOLCS, the Engine Oil Licensing and Certification System. ILSAC oils often carry the API Service Symbol (Donut) including the Energy Conserving designation and/or API Certification Mark (Starburst).
The latest ILSAC spec is GF-5 (GF-6 should be coming out in the next year or two).
ACEA stands for Association des Constructeurs Européens d'Automobiles (or European Automobile Manufacturers' Association in English). ACEA is the "European Standard" for motor oils. It is the main lobbying and standards group of the automobile industry in the European Union.
ACEA defines specifications for engine oil's "ACEA Oil Sequences". The sequences are usually updated every few years to include the latest developments in engine and lubricant technology. ACEA itself does not approve the oils, they set the standards and oil manufacturers may make performance claims for their products if those satisfy the relevant requirements.
Every ACEA specification is made of a letter or letters that indicate the class and a number that defines the category. There are separate categories for oils with different purposes or for different applications within the same class. There are ACEA specifications for passenger car motor oils (the A/B class) for catalyst compatible motor oils (the C class) and for heavy duty diesel engine oils (the E class). The classes are further divided into categories to meet the requirements of different engines.
For instance, the A/B class's A5/B5 oils have a lower HTHS (High-Temperature High-Shear) viscosity, which means that they provide better fuel economy but they may not provide adequate protection in engines that are not designed for them. ACEA A3/B3 and A3/B4 on the other hand require oils with higher HTHS viscosities that may not provide as good fuel economy as an A5/B5 oil but may offer better engine protection in certain engine designs.
Although it is true that the performance standards and requirements to meet the ACEA specs tend to be higher and more stringent than the minimum requirements set by API, as I mentioned before, many high quality synthetic oils available in North America do in fact meet the European ACEA specs.
What is an OEM oil specification?
A specification is an interface between an oil's physical and chemical properties and the car manufacturer's requirements. Car manufacturers combine a set of expected properties and test results in a specification while oil companies have their products tested for those requirements and show the earned specification or "approval" on the product as proof that their product is fit to be used where that particular spec is demanded.
Some car manufacturers will actually run very specific engine tests to make sure the oil used meets the specific requirements of their vehicles - these tests are in addition to those required by API or ACEA (which are minimum specs). Those OEMs will subsequently come out with a list of "approved motor oils" to be used in a specific engine or vehicle.
So OEM oil specifications are codes, which are used to match oils with cars. By choosing an oil based on a specification we make sure that we choose the right oil for our car.
To achieve full approval, lubricant manufacturers typically submit an oil sample to the OEM for testing, to ensure it complies fully with the specification. Testing is carried out by an independent laboratory or, in some cases, by the OEM. If the oil is fully compliant, the OEM issues a "certificate of approval" that usually lasts between one and five years. This certificate proves that the lubricant has undergone a rigorous approval and quality control process.
Note: Some manufacturers (e.g. KIA, Hyundai, Toyota) don't have an "OEM specific" certification or "approval" and only recommend a minimum API, ILSAC, and/or ACEA requirement that the motor oil should meet.
Why all the different OEM oil specs? Some are recommended for gasoline powered cars, others for diesels; some are for newer cars, some for older; some are for normal drain intervals, some are for extended drains. This means that not all of them demand similar performance levels from the motor oil.
There are higher end standards and lower end standards and it's good to know which one to choose if you want an oil that excels in as many areas as possible.
Here are some examples of different OEM Specs:
GM: dexos1 Gen 2; dexos2; LL-A-025; LL-B-025; 6094M; 4718M
Chrysler: MS-6395; MS-12633; MS-10725; MS-10850; MS-10902
Ford: WSS-M2C171-F1; WSS-M2C913-A; WSS-M2C913-B; WSS-M2C913-C; WSS-M2C913-D; WSS-M2C917-A; WSS-M2C931-C; WSS-M2C934-A; WSS-M2C937-A; WSS-M2C945-A; WSS-M2C948-B; WSS-M2C950-A
Volvo: VDS3; VDS4; VDS4.5
Renault: RN0700; RN0710; RN0720; RLD-4; RLD-3
BMW: LL-98; LL-01; LL-01 FE; LL-04; LL-12; LL-14+
Mercedes-Benz: 226.5; 226.51; 228.31 228.51; 229.1; 229.3; 229.31; 229.5; 229.51; 229.52
Volkswagen: 500.00; 501.01; 502.00; 503.00; 503.01; 504.00; 505.00; 505.01; 506.00; 506.01; 507.00; 508.00; 509.00
So is your head spinning yet?