Short answer
The ACEA A/B sequences are European oil quality categories for passenger car and light van gasoline (A) and diesel (B) engines without the reduced ash limits of the C categories. The current ones are A3/B4, A5/B5 and A7/B7. ACEA, the European automobile manufacturers’ association, publishes them and updates them periodically, and oil marketers self-certify against them.
Who ACEA is and how the sequences work
ACEA is the association of European vehicle manufacturers. Its European Oil Sequences describe minimum test performance for engine oils, and a product claim is written with the category and the edition year, such as A3/B4-23.
Unlike API licensing, ACEA claims are self-certified by the oil marketer under industry rules for testing and record keeping. Many European carmakers write their own approvals on top of the ACEA categories.
A3/B4 and A5/B5
A3/B4 describes stable, high-HTHS oils (at least 3.5 mPa·s) suitable for extended drains in many gasoline and direct-injection diesel engines. It remains one of the most widely cited categories on 5W-40 and 0W-40 European oils.
A5/B5 permits a lower HTHS viscosity, between 2.9 and 3.5 mPa·s, for engines designed for fuel-economy oils. It should not be used in engines that require the higher HTHS of A3/B4.
A7/B7 and the 2021 changes
The 2021 edition removed A3/B3 and introduced A7/B7, which builds on A5/B5 and adds protection against low-speed pre-ignition, a chain wear requirement and a turbocharger compressor deposit requirement.
The 2023 update reintroduced a diesel wear test for several legacy categories, including A3/B4 and A5/B5, but not for A7/B7.
Using ACEA A/B claims
If a manual lists an ACEA category, match it along with the viscosity grade. For vehicles with diesel particulate filters, the C categories or a carmaker’s low-SAPS approval are usually what is specified instead.
Where a carmaker approval such as an MB, VW or BMW sheet is listed, that approval takes priority over the generic ACEA category.
Frequently asked questions
What does the slash in A3/B4 mean?
It indicates the oil meets both the gasoline (A3) and light diesel (B4) requirements in one combined category.
Is A5/B5 better than A3/B4?
They are different, not ranked. A5/B5 allows lower HTHS viscosity for fuel-economy engines, while A3/B4 requires higher HTHS.
General maintenance information. Always follow your vehicle or equipment manufacturer’s requirements and the current product data. Questions? Email [email protected].