ACEA Oil Specifications Explained: A3/B4, A5/B5, C2, C3, C5 and More
ACEA specifications are the European performance standards for engine oil, set by the European Automobile Manufacturers' Association. They sit alongside the viscosity grade and tell you what the oil is designed to do: protect a high-performance engine, save fuel, or protect a catalytic converter or diesel particulate filter.
The three ACEA families
- A/B: oils for petrol (A) and light diesel (B) engines, with no low-SAPS limits.
- C: catalyst-compatible oils with limited SAPS, for engines with diesel particulate filters (DPF), gasoline particulate filters (GPF) and modern catalysts.
- E: oils for heavy-duty diesel engines in trucks, buses and plant.
What is SAPS and why does it matter?
SAPS stands for sulphated ash, phosphorus and sulphur. These come from additives that protect against wear, but the small amount of oil that burns in the engine leaves ash behind. That ash can block a DPF and shorten the life of a catalyst. C category oils limit SAPS: C1 and C4 are low-SAPS, while C2, C3, C5 and C6 are mid-SAPS.
A/B categories
| Category | What it means |
|---|---|
| A3/B4 | High-performance oil with full SAPS and a high-temperature high-shear (HTHS) viscosity of at least 3.5 mPa·s. Common in 5W-40 and 10W-40 for petrol and diesel engines without a particulate filter. |
| A5/B5 | Fuel-economy oil with a lower HTHS viscosity, between 2.9 and 3.5 mPa·s. Common in 0W-30 and 5W-30 for engines designed for it, such as many Ford and Volvo engines. Not suitable for engines that need A3/B4. |
| A7/B7 | Introduced in 2021. A fuel-economy oil like A5/B5, with extra protection against low-speed pre-ignition (LSPI) and wear in modern turbocharged direct-injection petrol engines. |
C categories
| Category | SAPS level | HTHS viscosity | Typical use |
|---|---|---|---|
| C1 | Low | 2.9 mPa·s or more | Fuel-economy oil for some Ford and Jaguar Land Rover engines. |
| C2 | Mid | 2.9 mPa·s or more | Fuel-economy oil for many Peugeot, Citroën, DS and Fiat engines. |
| C3 | Mid | 3.5 mPa·s or more | The most widely used C category. VW 504 00 / 507 00, BMW Longlife-04 and MB 229.51 are all built on it. Usually 5W-30 or 5W-40. |
| C4 | Low | 3.5 mPa·s or more | Renault diesel engines that need RN0720, and some Mercedes-Benz engines. |
| C5 | Mid | 2.6 mPa·s or more | Low-viscosity fuel-economy oil, usually 0W-20, for newer engines designed for it, such as those needing VW 508 00 / 509 00. |
| C6 | Mid | 2.6 mPa·s or more | Introduced in 2021. Like C5, with added LSPI protection for the latest downsized turbo petrol engines. |
E categories for trucks and plant
ACEA E4, E6, E7, E8, E9 and E11 cover heavy-duty diesel engines. E6, E8, E9 and E11 are designed for engines fitted with particulate filters. See our truck and commercial engine oils.
ACEA or manufacturer approval: which matters more?
If your handbook names a manufacturer approval, such as VW 504 00 or MB 229.51, choose an oil carrying that approval. Approvals are built on ACEA categories but add the car maker's own engine tests. If your handbook only lists an ACEA category, any oil meeting that category in the right viscosity grade is suitable. Read more in manufacturer oil approvals explained.
Can I swap one ACEA category for another?
No. Each category is designed for a different type of engine. A C3 oil is not a substitute for C5, and an A5/B5 oil is not a substitute for A3/B4. Many oils meet more than one category, and their labels list every category they meet, so check that yours is on the list.
Frequently asked questions
What does ACEA C3 mean?
C3 is a mid-SAPS, catalyst-compatible ACEA category with a high-temperature high-shear viscosity of at least 3.5 mPa·s. It suits many modern petrol and diesel engines with particulate filters, and it is the base for several major manufacturer approvals. Most C3 oils are 5W-30 or 5W-40.
Do I need a C category oil if my car has a DPF?
In almost all cases, yes. Diesel cars with a DPF need a low or mid-SAPS oil, and your handbook will name the exact category or approval.
What is API, and does it matter in the UK?
API is the American Petroleum Institute's system. Petrol ratings start with S, such as SN, SP and the newer SQ, and diesel ratings start with C. European cars usually call for ACEA categories or manufacturer approvals, while API and ILSAC ratings are more common in Japanese, Korean and American cars.
What is HTHS viscosity?
High-temperature high-shear viscosity measures how thick the oil stays under the heat and pressure inside engine bearings. A higher figure means a stronger oil film, and a lower figure means less friction and better fuel economy.