ACEA oil specifications versus API ILSAC oil specifications

ACEA oil specifications versus API ILSAC oil specifications

On Reddit forums, I routinely see questions from European car owners asking why Americans change their oil so often compared to what’s done in Europe. They ask the question, implying that Americans are somehow being “duped” into changing their oil more often. That’s not the case at all. European cars have longer oil change intervals because they use a different oil than we use in the U.S. Our oil specifications are set by the trade association American Petroleum Institute (API) in conjunction with the International Lubricant Standardization and Approval Committee (ILSAC), which is a joint effort between American and Japanese carmakers. To understand the differences in the oils used in American and Japanese versus European cars, you must first understand the differences between ACEA oil specifications versus API ILSAC Oil Specifications.

Carmaker input into oil specifications

Carmakers and oil and gas industries have significant input into API and ILSAC oil specifications. Only carmakers have input into ACEA oil specifications. Even then, many European carmakers go beyond ACEA specifications and require proprietary oils for certain engines and model years. However, this is starting to change in the U.S. as well with GM specifying Dexos oil for use in GM vehicles. GM Dexos oil goes beyond API specifications.

Diesel and gasoline engines need a different oil

Europeans drive diesel-powered vehicles versus American and Japanese gasoline-powered vehicles.  In Europe, most vehicles are equipped with diesel particulate filters (DPF) to reduce soot emissions, so the oils they use must be compatible with DPF systems to prevent DPF fouling. Since diesel engines create more contaminants, ACEA oils contain more detergents and dispersants than an API ILSAC oil would for comparable gasoline engines. The additional detergent would interfere with an API test, and would actually cause the oil to fail API testing schemes.

Due to the prevalence of diesel engines, ACEA requires that all oil must work with diesel and gasoline engines alike. In fact, ACEA does not even allow an oil specification for gasoline engines only. API and ILSAC, on the other hand, have separate oil specifications for gasoline and diesel oils.

Longer drain intervals mean different additive packages

In addition to working with both diesel and gasoline engines, the additive packages in ACEA oil must last throughout the longer oil change intervals specified by ACEA (12,500 to 31,000 miles). That’s an important point since neither API nor ILSAC specifies oil change intervals. That is left up to the discretion of the carmakers.

Differing emissions and fuel economy issues between ACEA and API ILSAC

ACEA oil specifications tend to focus on low viscosity and extended drain intervals to meet Euro IV/Euro V emissions requirements. ACEA oil is formulated to protect the life of the diesel particulate filters. API, on the other hand, is more concerned with developing oil specifications that protect three-way catalytic converters and meet higher fuel economy standards. So API oils limit the amount of phosphorus (anti-wear additives) and sulfur to protect the catalytic converter. API and ILSAC oil must also be formulated to work well with a high degree of ethanol content in the American fuel supply chain. ACEA oils do not even address the ethanol issue.

ACEA versus API ILSAC testing procedures

ACEA, API, and ILSAC engine test sequences measure the same parameters: engine sludge, cam wear, oil oxidation, engine varnish, ring sticking, etc. But the test engines and testing hardware are different between the ACEA and API ILSAC tests. So the oil needed to pass the tests must also be different.


Due to the prevalence of diesel engines in Europe, ACEA oils are formulated more to handle the demands of a diesel engine, meet the much longer drain intervals demanded by ACEA, while preventing harm to the diesel particulate filter systems. API and ILSAC focus more on working well with gasoline engines while protecting the catalytic converter, providing increased fuel economy and affording compatibility with ethanol and turbochargers.

©, 2021 Rick Muscoplat

Posted on by Rick Muscoplat


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