Engine oils sold around the world are classified against two main families of standards: the American system and the European system. Both exist to make sure an oil meets defined quality and performance requirements, but they are developed by different bodies and test different things.
The American system
In North America, engine oil performance categories are defined by the American Petroleum Institute (API), with test methods developed by bodies such as ASTM. API categories such as API SP (petrol engines) and API CK-4 (heavy-duty diesel) tell you which engines an oil is designed for. ILSAC ratings such as GF-6 add fuel-economy requirements for passenger cars.
The European system
In Europe, oil sequences are defined by ACEA, the European Automobile Manufacturers' Association. ACEA sequences reflect European engine designs, longer drain intervals and stricter emissions systems. They are grouped into A/B (petrol and light diesel), C (catalyst-compatible, low-SAPS oils for engines with after-treatment) and E (heavy-duty diesel).
Key differences
- Engine design: European engines are often smaller, higher-revving and turbocharged, and many run on diesel, so ACEA tests focus heavily on high-temperature protection and deposit control.
- Drain intervals: European standards are written with longer oil-change intervals in mind.
- Emissions systems: ACEA C-sequences limit sulphated ash, phosphorus and sulphur (SAPS) to protect particulate filters and catalysts.
- Fuel economy: API and ILSAC categories put strong emphasis on fuel economy for passenger cars.
Which should you follow?
Always follow the standard your vehicle manufacturer specifies in the owner's manual. Many BAROX oils carry both API and ACEA ratings, as well as OEM approvals, so you can match the right oil to your engine with confidence.
