What are the main international classifications of motor oils?

There are two main international classifications that serve as the basis for many car manufacturers’ approvals.:

• API (American Petroleum Institute);
• ACEA (European Automobile Manufacturers’ Association).

API (American Petroleum Institute). This classification mainly focuses on the performance properties of the oil, determining its suitability for gasoline and diesel engines.

For gasoline engines. It is indicated by the letter “S” (Service) followed by a letter indicating the oil generation (for example, API SA, SB, SC… up to modern API SP).

Each new generation is more advanced and has better engine protection, cleaner parts, and compatibility with modern systems.

For diesel engines. It is indicated by the letter “C” (Commercial) followed by a letter (for example, API CA, CB… before modern API CK-4).

Universal oils. They can have a combined designation, for example, API SN/CF, where SN is for gasoline, CF is for diesel.

ACEA (European Automobile Manufacturers’ Association). This European classification is stricter, it is focused on real-world operating conditions, as well as on the requirements of European automakers.

ACEA divides the oils into categories:

• A/B. For gasoline and diesel engines of passenger cars (for example, ACEA A3/B4).
• C. For gasoline and diesel engines with exhaust gas neutralization systems (Low SAPS – with a reduced content of sulphated ash, phosphorus and sulfur), for example, ACEA C3.
• E. For diesel engines of heavy machinery (trucks). ACEA takes into account aspects such as anti-wear properties, piston cleanliness, fuel economy, and compatibility with diesel particulate filters (DPF) and catalytic converters.