ACEA vs API Engine Oil: What’s the Difference?

Why Engine Oil Types Matter More Than You Think

As an automotive expert, I am often asked why American drivers change their engine oil more frequently than those in Europe. Some people assume we’re getting tricked into changing our oil more often. However, the truth is that it ultimately comes down to the type of engine oil, the specific oil grades, and the performance expectations set by various oil specifications, such as ACEA, API, and ILSAC.

Understanding the differences in oil rating systems and the requirements for oil viscosity is critical. European automakers design their engines around ACEA standards, while American and Japanese automakers rely on API and ILSAC standards. This is not just a difference in branding—it’s a fundamental difference in how oils are formulated, tested, and used.

Who Sets Engine Oil Standards?

API and ILSAC Engine Oil Standards: Driven by Fuel Economy and Emissions

In North America, engine oil types are governed by the oil

Look for these symbols on the motor oil you buy

rating standards set by the American Petroleum Institute (API) and the International Lubricant Standardization and Approval Committee (ILSAC). These groups work with automakers—mainly from the U.S. and Japan—to ensure that oil grades meet fuel economy requirements, emissions targets, and durability expectations for gasoline engines.

The North American focus primarily involves protecting catalytic converters, handling ethanol-laden fuel, and minimizing turbocharger deposits—all while maintaining proper oil viscosity under varying driving conditions.

ACEA: European Carmakers in Control

In Europe, the engine oil rules are entirely different. The Association des Constructeurs Européens d’Automobiles (ACEA) sets the standards for engine oil types. ACEA is comprised of 15 European vehicle manufacturers, and their approach focuses primarily on engine longevity, extended oil grades for longer drain intervals, and compatibility with diesel particulate filters (DPFs).

In essence, ACEA oils are engineered to meet the specific demands of both diesel and gasoline engines in Europe, with an emphasis on longer service intervals and environmental protection standards that differ from those in North America.

Key Differences Between ACEA and API/ILSAC Engine Oils

Diesel Dominance Drives European Oil Standards

ACEA requires that all engine oils meet standards for both gasoline and diesel engines—there’s no separation. This significantly impacts the formulation of engine oil types.

Because diesel engines generate more combustion byproducts, ACEA oils contain more detergents and dispersants than API-certified oils. This higher detergent level would cause an oil to fail API’s testing protocols, yet it’s crucial for European engines.

Additives Tailored for Long Drain Intervals— ACEA oils are designed with long-lasting additive packages to support drain intervals of 12,500 to 31,000 miles, compared to typical North American intervals of 5,000 to 7,500 miles. These additives are balanced to maintain oil viscosity, prevent sludge, and protect after-treatment systems like DPFs.

SAPS: The European Balancing Act

SAPS stands for Sulfated Ash, Phosphorus, and Sulfur, key components in additive packages that define an engine oil type’s ability to protect the engine.

Sulfated Ash— This represents the leftover non-combustible material from anti-wear and detergent additives. Too much ash leads to clogged diesel particulate filters (DPFs) and engine wear.

Phosphorus— A powerful anti-wear agent that also limits friction. However, excess phosphorus can poison catalytic converters.

Sulfur— Provides antioxidant and detergent properties but, like phosphorus, poses risks to exhaust after-treatment systems if used in high quantities.

Understanding ACEA Oil Ratings

ACEA E4 & E6: For extended drain intervals. E4 is high-SAPS, E6 is low/mid-SAPS.

Click on the image to go to the ACEA website.

ACEA E7 & E9: For standard intervals. E7 is high-SAPS, E9 is mid/low-SAPS.

ACEA A/B: A for gasoline light-duty, B for diesel light-duty.

These oil ratings dictate the formulation and the balance of detergent, dispersant, and anti-wear additives.

Why Oil Grades and Oil Viscosity Vary

The Role of Viscosity and Additives

European ACEA oils prioritize maintaining oil viscosity under high loads and long intervals. API/ILSAC, in contrast, places stricter limits on phosphorus and sulfur to protect catalytic converters in gasoline vehicles.

U.S. oils are also engineered to handle ethanol, which is widely used in North American fuels. European oils don’t account for ethanol because it’s not a major fuel component there.

Diesel and gasoline engines need different oil

Europeans drive diesel-powered vehicles, whereas Americans and Japanese drive 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 oil specifications for gasoline engines. 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 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.

Testing: API vs. ACEA Procedures

While both API/ILSAC and ACEA test for sludge, oxidation, cam wear, and ring sticking, they use different engines and testing methods. That means an oil formulated to pass API’s standards won’t necessarily meet ACEA’s, and vice versa. The demands on oil viscosity, anti-wear performance, and oil grades are tailored to each region’s engineering philosophies.

©, 2021 Rick Muscoplat