Classification of engine oils

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Lubricants must be able to guarantee a minimum quality according to the application and to define a specific "performance" value that is verified and defined both by laboratory tests and in the filed, using a fleet of motor vehicles.

Performance classification is often established by international bodies that develop, publish and regularly update the so-called "specifications" on the basis of lubrication needs as expressed by the market and in line with the evolution of engine technology. In many cases, the manufacturers of vehicles and/or engines or national bodies (e.g. the army, navy, etc.) produce their own specifications.

Leading international associations (API, ACEA, ILSAC and others) have established a classification based on performance that is integrated with that of the biggest manufacturers of motor vehicles who in turn establish their own specifications.

The classification adopted in the United States and issued by the (American Petroleum Institute), is divided into two groups: "S" for petrol driven engines; "C" for diesel engines. These letters are followed by second letter that indicates lubricant performance (e.g. SJ).
In Europe, the ACEA (Association des constructeurs Européens d'Automobiles), the association that brings together the leading European car manufacturers, has defined the categories and applications for motor oils for petrol-driven cars with the letter "A", for diesel engines with the letter "B" and for commercial diesel vehicles the letter "E". A further category, defined with the letter “C‘, is the one for Low SAPS products or diesel particulate filter compatibility.

In general, the performance specifications for lubricants tend to increasingly guarantee:

  • Longer gaps between oil changes -> a tendency to use synthetic bases
  • Lower friction in moving parts -> lower viscosity
  • A reduction of ash-forming components
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