Choosing the right engine oil can feel overwhelming. With so many numbers and letters on the label — like ACEA C3, VW 504 00, MB 229.51, or BMW LL-04 — it’s not always clear which one is right for your car.
In this guide, we’ll break down the main oil specifications, explain what they mean, and show you how to match the correct oil to your vehicle.
1. Industry Standards: ACEA, API & ILSAC
The ACEA (European Automobile Manufacturers Association) sets quality standards for oils sold in Europe.
ACEA Oil Categories
- A/B = Petrol & light-duty diesel engines
- C = “Catalyst/DPF safe” (low SAPS oils that protect modern emissions systems)
- E = Heavy-duty diesel (trucks, buses, vans)
Common ACEA Ratings
- ACEA A3/B4 → High protection, for older engines without DPF
- ACEA A5/B5 → Fuel-saving, thinner oils (long-drain capable, not ideal for DPF)
- ACEA C2 → Mid SAPS, fuel economy oils for modern cars with DPF
- ACEA C3 → Mid SAPS, strong protection, common in modern petrol & diesel with DPF
- ACEA C4 → Low SAPS, specialist Renault/other vehicles
Tip: If your car has a DPF (diesel particulate filter), you’ll usually need a C-grade oil (C2, C3, C4).
2. Manufacturer-Specific Approvals
Car makers go beyond ACEA standards and set their own approvals. These ensure the oil works with their engines, emissions systems, and service intervals.
Volkswagen / Audi / Skoda / SEAT (VAG Group)
- VW 502 00 → Petrol engines, fixed service intervals
- VW 505 00 → Diesel, fixed intervals
- VW 505 01 → PD (unit-injector) diesel engines
- VW 504 00 → Petrol, long-life flexible service intervals
- VW 507 00 → Diesel, DPF safe, long-life intervals
- VW 508 00 / 509 00 → New generation 0W-20 oils for ultra-efficient engines
Mercedes-Benz
- MB 229.3 → Quality petrol/diesel oils
- MB 229.5 → High protection, extended drain
- MB 229.51 → DPF safe (low SAPS)
- MB 229.52 → Latest generation, DPF safe
BMW
- BMW LL-01 → Long-life petrol/diesel
- BMW LL-04 → DPF safe, common in modern diesels
- BMW LL-12 FE / LL-14 FE+ / LL-17 FE+ → Fuel-efficient, newer engines, 0W-20 or 0W-30 oils
Ford
- Ford WSS-M2C913 A/B/C/D → Older 5W-30 oils
- Ford WSS-M2C948-B → 5W-20 EcoBoost petrol
- Ford WSS-M2C950-A → 0W-30 for modern diesels
Other Common Approvals
- GM Dexos2 → Opel/Vauxhall/GM, DPF safe
- Renault RN0720 → Diesel with DPF
- PSA B71 2290 → Peugeot/Citroën DPF safe
3. Viscosity vs Specification
It’s important to understand that viscosity (0W-20, 5W-30, 5W-40, etc.) and oil specification (ACEA C3, VW 504/507, etc.) are two separate things.
- Viscosity = How thick the oil is at different temperatures (important for cold starts & protection).
- Specification = The performance and compatibility standards the oil meets.
You must match both the viscosity and the specification listed in your vehicle’s manual.
4. Quick Rules for Choosing the Right Oil
- Always check your vehicle handbook first.
- If your car maker lists a specific approval (VW 504 00, MB 229.51, etc.), choose an oil that carries that approval.
- If no manufacturer approval is listed, follow the ACEA specification.
- For cars with a DPF, stick to ACEA C-spec or the manufacturer’s DPF-safe oil.
5. Conclusion
Understanding oil specifications doesn’t have to be complicated.
- ACEA/API = General industry quality standard
- Manufacturer approval (VW, BMW, MB, Ford, etc.) = Exact requirement for your engine
By matching both the viscosity and the correct approval/ACEA spec, you’ll protect your engine, improve fuel efficiency, and keep your car running smoothly for longer.
At Cox Motor Parts, we stock a full range of ACEA and manufacturer-approved oils including VW 504/507, BMW LL-04, MB 229.51, and Ford WSS specifications.
Browse our engine oils here
Frequently Asked Questions (FAQs)
What does ACEA C3 oil mean?
ACEA C3 oil is a mid-SAPS, low-ash engine oil designed for modern petrol and diesel engines fitted with catalytic converters and diesel particulate filters (DPFs). It provides strong engine wear protection while being emissions-system safe.
Can I use ACEA C2 instead of C3?
No, not always.
- ACEA C2 oils are designed for fuel economy and are usually thinner, which some engines are not designed for.
- ACEA C3 oils are more protective, slightly thicker at high temperatures.
– Always check your car’s handbook. If it specifically says C3, don’t replace it with C2.
What’s the difference between VW 504 00 and VW 507 00?
- VW 504 00 = For petrol engines, long-life service intervals.
- VW 507 00 = For diesel engines, DPF safe, long-life service.
– Many modern VW Group oils are dual-approved 504/507, so they cover both.
What oil does VW 508 00 / 509 00 refer to?
VW 508 00 / 509 00 is a newer generation 0W-20 oil designed for ultra-efficient VW Group engines. It should not be mixed with 504/507 oils unless explicitly allowed by VW.
What happens if I use the wrong oil specification?
Using the wrong oil can cause:
- Poor engine protection
- Increased wear and deposits
- DPF or catalytic converter damage (if you use non-low-SAPS in a DPF car)
- Possible voiding of manufacturer warranty
Is viscosity (5W-30, 0W-20, etc.) the same as specification?
No. Viscosity is about oil thickness (temperature behaviour), while specification is about quality and compatibility standards (ACEA/API/OEM). You must match both.
Can I mix different oils?
Mixing different oils in an emergency is usually safe as long as the viscosity is similar (e.g. both 5W-30). However, for best performance and warranty compliance, always top up with an oil that meets your car’s exact specification.
Final Word
When it comes to engine oils:
- Match your manufacturer approval first (VW 504/507, MB 229.51, BMW LL-04, etc.)
- Check ACEA spec if OEM approval isn’t listed
- Always stick to the recommended viscosity
Need the right oil? Browse our full engine oil range here
