Short answer
The ACEA C categories describe European engine oils with reduced sulfated ash, phosphorus and sulfur (SAPS), meant for gasoline and diesel engines with modern aftertreatment such as particulate filters. Current categories run from C2 through C7 and differ mainly in ash level and high-temperature high-shear (HTHS) viscosity. C7, added in 2023, is the newest and is aimed at 0W-16 fuel-economy oils.
Why the C categories exist
Ash from engine oil additives collects in diesel and gasoline particulate filters and cannot be burned off during regeneration. Phosphorus and sulfur can also affect catalyst performance over time.
The C categories cap these elements so oils are compatible with aftertreatment systems, while still setting engine test requirements for wear, deposits and oxidation.
C2 through C5
C3 is a mid-SAPS category with an HTHS viscosity of at least 3.5 mPa·s, and it underlies many carmaker approvals such as VW 504 00/507 00 and GM’s old dexos2. C4 is a lower-ash category with the same HTHS floor, used by some carmakers that need very low ash.
C2 and C5 are mid-SAPS categories that allow lower HTHS viscosity for fuel-economy engines, with C5 allowing the lowest HTHS of those four. They should not be used where a manual calls for C3 or C4.
C6 and C7
C6 arrived in the 2021 edition. It builds on C5 and adds low-speed pre-ignition protection, chain wear and turbocharger deposit requirements, plus a fuel economy test.
C7, added in 2023, is based on C6 but with stricter fuel economy requirements and is intended for ultra-low-HTHS oils such as 0W-16. ACEA C1 was retired in 2021 due to limited use.
Reading a C-category claim
Claims are written with the edition year, such as C3-23. Check that the category on the oil matches the manual, and remember that carmaker approvals such as BMW LL-04 or MB 229.52 are separate from the ACEA claim.
Low SAPS is not automatically better. Engines designed for full-ash oils may list A/B categories, and engines needing high HTHS should not get a low-HTHS C category.
Frequently asked questions
Is ACEA C3 the same as VW 504 00/507 00?
No. VW 504 00/507 00 is built on similar chemical limits but requires VW’s own approval testing.
Can I use a C5 oil where C3 is specified?
Generally no. C5 allows lower HTHS viscosity than C3 requires. Use the category in the manual.
General maintenance information. Always follow your vehicle or equipment manufacturer’s requirements and the current product data. Questions? Email [email protected].
