Lubricants - Properties and features

A lubricant is qualified for a specific application by the properties required for that use. These properties are set out in a specification, standard or norm. Some of them are summarized in technical data sheets intended for users. The composition of the products is never given. In some cases, the presence in the formula of valuable or original constituents (synthetic bases, very high VI hydrotreated bases, new additives, etc.) is mentioned, enabling the product to be better promoted, but the indication always remains rather vague as to the exact nature of the components and in no case provides information on their concentrations.

Properties fall into two groups: identification and use characteristics, and performance characteristics.

Identification (density, refractive index, pour point, etc.) and use characteristics are physical and/or chemical properties, usually referred to as "physico-chemical properties", assessed by simple laboratory tests. Some of these characteristics are actually functional properties (usage characteristics), such as compressibility or dynamic viscosity.

Physico-chemical, mechanical or complex performance characteristics are assessed by tests carried out in the laboratory, in cells on test benches or in actual service.

This article describes only the most commonly used properties and characteristics of both liquid lubricants and greases. A complete list of all test and analysis methods is given in the documentation at the end of the study, together with the equivalences between the various national and international standardization bodies.