www.EngineOilInfo.com - Service Class/Category

There are many different engine oil classification systems currently in use. Three that are commonly used are API, ILSAC, and ACEA classification systems. Engine oil packaging will often list multiple rating systems. The first letter signifies the service class, e.g., diesel or gasoline engine. The second number or letter signifies the intended category for different applications within that general class and indicates some aspects of the performance level of the oil. In most, but not all cases, the latest rating is backward compatible. This means that the latest service class, such as API SM, meets the specifications of previous service classes and can be used in older engines. This chart lists the latest service classifications for the three most widely used systems:

We recommend following the engine manufacturer's recommendations for appropriate service class/category specifications.

American Petroleum Institute (API) Service Categories
(See 'Helpful Links' for a PDF of the API Engine Oil Guide that details all API service categories.)

API represents North American oil manufacturers. For automotive gasoline engines, the most recent API service category is SM (introduced in 2004). This service category includes the performance properties of each earlier category. If an automotive owners manual calls for an oil with earlier API service category, an API SM oil will provide full engine protection. Consumers can identify oils meeting the latest automobile manufacturers' recommendations by looking for oils displaying the API Service Symbol "Donut" with the API Service SM.

For diesel engines the most recent service category is CJ-4 (introduced in 2006). The latest category for diesel engines usually, but not always, includes the performance properties of an earlier category.

European Automotive Manufacturers Association (ACEA) Categories
(See 'Helpful Links' for a PDF of the ACEA European Oil Sequences Guide that details all ACEA rating specifications.)

ACEA represents Western European automobile and heavy-duty truck manufacturers. The organization uses different engines for testing than those used by API and SAE, and the requirements necessary to meet the ACEA standards are different yet generally correspond with most API ratings.

The ACEA rating uses A1 through A5 for gasoline engine oil ratings and B1 through B5 for diesel engine oil ratings. Starting in 2004, ACEA began using combined ratings such as A1/B1, A3/B3, A3/B4 and A5/B5. Catalyst Compatible oils for Gasoline and Diesel engines with after-treatment devices are designated with C1 through C4, and heavy duty diesel engine ratings are E2 through E7.

The International Lubricant Standardization and Approval Committee (ILSAC) Ratings
ILSAC represents North American and Asian automobile manufacturers. ILSAC developed an oil rating that consolidates the SAE viscosity rating and the API quality rating. If an engine oil meets the standards, a certification mark "Starburst" symbol is displayed on the front of the oil container. If the starburst is present it is an indication that the oil is suitable for use in almost any gasoline engine. The original GF-1 (gasoline fueled) rating was updated to GF-2 in 1997, GF-3 in 2000 and GF-4 in 2004.

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