Function and composition of lubricants
The main use of lubricants in motor vehicles (as well as in industrial machinery) is the reduction of friction and wear from mechanical contact and heat.
Friction is the force that opposes movement on two surfaces, while wear is that change that takes place on a surface due to the removal of abrasive debris as a result of mechanical contact, as well as of a chemical-physical nature due to the heat generated by friction.
A lubricant is a balanced mix of a number of components. The composition of this mix, in other words the recipe that a production (blending) plant must follow, is called the "formulation".
The formulation of a lubricant is made up of base oils and additives that combine to determine behavior when in use, both in terms of performance and in terms of duration.
The final quality of lubricating oil usually depends on the quality of the base oils used, which are generally distinguished as either:
- mineral oils: obtained from the distilling process in the refining of crude oil
- synthetic oils: which are derived from particular physical/chemical laboratory treatments.
Compared with mineral base oils, synthetic base oils guarantee:
- A lower level of volatility to a comparable level of viscosity (which leads to lower consumption during use).
- A higher viscosity index (a wider temperature gap).
- Greater chemical stability at high temperatures (longer useful life).
The use of a synthetic base oil in the formulation of a lubricant is generally defined by the performance requirements of manufacturers (regarding volatility, viscosity, longer life), by environmental considerations (non toxicity, biodegradability) or by marketing demands (synthetic oil = high technology oil).