Guide to oil codes: ACEA, API and OEM explained

On an engine oil label you will often find codes such as ACEA A3/B4, API SN or manufacturer codes such as VW 504.00 or BMW LL-04. They are not random numbers: they tell you whether that oil is really suitable for your engine. Here is a simple guide to understanding them.

What ACEA means

ACEA (European Automobile Manufacturers' Association) is the European reference standard for engine oils. The main categories are:

  • A/B — petrol and diesel engines for cars and light vans (e.g. A3/B4: high performance, extended use)
  • C — engines with new-generation catalytic converters/particulate filters ("low SAPS" oils, compatible with exhaust after-treatment systems)
  • E — heavy-duty diesel engines (trucks, commercial vehicles)

The number after the letter (e.g. A3, C3) indicates the performance level within the category: a higher number generally means a more recent or stricter specification.

What API means

API (American Petroleum Institute) is the equivalent American standard. The most common codes:

  • S.. (e.g. SN, SP) — petrol engines ("Service")
  • C.. (e.g. CK-4) — diesel engines ("Commercial")

Here too, the letter after the S or C indicates the evolution of the specification: letters further along the alphabet are generally the most recent.

What OEM approvals are

In addition to the general ACEA/API standards, each car manufacturer can require its own stricter or specific requirements for its engines: these are OEM (Original Equipment Manufacturer) approvals, e.g. VW 504.00/507.00, BMW LongLife-04, Mercedes-Benz 229.5, Ford WSS-M2C913, Stellantis/PSA B71 2312. If your car's manual requires a specific approval, the chosen oil must meet it: it is not enough for it to fall generically within an ACEA or API category.

The approvals covered in our catalogue

Each car manufacturer has its own codes. Here is what the ones you will most often find on the products in our catalogue mean — useful for understanding what you are reading, not a substitute for checking your owner's manual:

  • Volkswagen / Audi / Seat / Skoda — 504.00/507.00 is the group's strictest "low SAPS" standard (since 2004), designed for petrol and diesel engines with particulate filters and long service intervals; 502.00/505.00/505.01 are older approvals (high-performance petrol engines, older diesels including pump-injector units); 501.01 is the oldest standard, for petrol or diesel engines without a particulate filter. The two groups are not interchangeable: what counts is always the exact approval required by the manual.
  • Mercedes-Benz — the 229.5 family (229.51, 229.52) indicates "low SAPS" oils with low sulphur/phosphorus/ash content, designed to protect exhaust after-treatment systems (petrol and diesel particulate filters, catalytic converters) on engines that require them.
  • BMW — Longlife-04 (LL-04) is the "low SAPS" specification for diesel engines (with or without particulate filter) and petrol engines with particulate filter; typical grades 0W-30, 0W-40, 5W-30, 5W-40.
  • Ford — the WSS-M2C913 (A/B/C/D) family covers petrol and light diesel engines with SAE 5W-30 oils; the letters indicate the evolution of the specification over time (from the oldest 913-A to the most recent 913-D, also designed for engines compatible with diesel containing a biodiesel component).
  • GM / Opel — dexos2 is the global GM standard for European petrol and diesel engines from 2011 onwards, built on ACEA C3 with additional GM-specific tests.
  • Porsche — C30 is a manufacturer-specific approval for part of the engine range, with a list of officially tested and approved oils.
  • Fiat / Stellantis (Selenia) — the 9.55535 family has several variants (S1, S2, S3, GS1, DS1/DH1, N2/N3, DM1, DSX and others) linked to engine, grade and engine generation. Important update: since early 2024 Stellantis has introduced the new FPW9.55535/03 (5W-30) specification for the 1.5 BlueHDi/Multijet diesel engines (DV5R Euro 6D) of Peugeot, Citroën, DS, Opel/Vauxhall and Fiat, replacing the previous recommendations (0W-30/0W-20), to reduce a known issue of timing chain noise and wear. If you drive one of these models with an engine of that generation, check the most up-to-date specification with us on WhatsApp before buying.
  • PSA / Stellantis — B71 2290 and B71 2312 are the group's specific approvals for latest-generation petrol engines (including the PureTech three-cylinder turbo engines), often paired with 0W-20 or 5W-30 grades depending on the engine.
  • Manual gearbox and differential (API GL-4 / GL-5) — they are not interchangeable: GL-4 has a milder EP (extreme pressure) additive package, suitable for manual gearboxes with brass/bronze synchronisers that GL-5 could corrode; GL-5 has more aggressive EP additives, designed for differentials and hypoid-gear axles under high load. Some products declare both approvals because they are formulated to be safe for both uses: still check what your gearbox manual requires.

As with the other codes, these lists describe what the approvals mean, not which specific engine in your car requires them: the exact match depends on the engine code, the year of production and sometimes the market, and can change — as in the Stellantis case above — even after you buy the car. The most reliable source remains the owner's manual or a direct check with us.

How to read them together

On the packaging you will usually find all three pieces of information together, for example: SAE 5W-30 — ACEA C3 — API SN — approved VW 504.00/507.00. This means: viscosity grade 5W-30, compliant with the European C3 standard (low SAPS), compliant with the American SN standard, and officially approved by Volkswagen for that group of engines.

Why choosing correctly matters

Using an oil with the wrong specification is not just a question of performance: on engines with a particulate filter or direct injection it can cause real damage over time. That is why we state the technical specification on every Auto Evo Store product page, and if you have any doubts about compatibility with your car you can write to us directly on WhatsApp before ordering: together we will check the right code for your manual.

Our commitment

That is why we always recommend checking compatibility before ordering, by messaging us on WhatsApp with your registration plate, registration document or the OE/OEM code: it is the safest way to avoid a wrong purchase. If the product still turns out to be unsuitable, you have the right to return it within 14 days of delivery, provided it is intact and in its original packaging: return shipping costs are paid by the customer, except in the case of a defective product or a shipping error attributable to us.