A lubricant consists of 70-100% base lubricants and up to 30% chemical compounds known as additives, which are fully mixed.
The above components of crude oil can be integrated into more general categories. Some of them impart desirable properties to lubricants while some have harmful properties and effects. Hydrocarbons are called the mainstream organic components of “crude” oil, consisting solely of carbon and hydrogen.
- Alkanes or paraffins, with saturated linear or branched carbon chains in single bonds,
- Alkenes or olefins, with saturated (or unsaturated) molecules in double bonds of carbon,
- Ali-cyclic hydrocarbons or naphthenes, saturated cyclic structures consisting of five or six carbon atoms in single bonds between them,
Aromatic hydrocarbons, circular structures with double bonds which rely heavily on the sixfold benzene ring (C6Η6).
Having as a criterion the basic content of crude oil in alkanes/paraffins (crystalline texture hydrocarbons, solid at normal atmospheric temperature with a colour close to white) and asphalt (crystalline or semi-solid compounds of ‑black or black-brown colour consisting of polycyclic aromatic hydrocarbons), we distinguish three main categories of crudes:
- Oils of paraffinic base
They have low specific gravity, contain paraffin, little or no asphalt and give away a great proportion of mineral oils. In this category we have the oils of N. Pennsylvania and the North Sea.
- Oils of asphaltic and naphthenic base
They have high specific gravity, contain asphalt, little or no paraffin and give away a small proportion of mineral oils. The oils of Nigeria, California, Mexico, the Mexican Gulf and Venezuela belong to this category.
- Oils of mixed base
They contain asphalt and paraffin and the overwhelming majority (90%) of oils (e.g. oils of the Middle East and East Texas, USA) belongs to this category.
It is worth noting that the “crude” oil coming from various oil wells differs in texture, not only from place to place, but even in the same area. In oil refineries, the “crude” oil is subjected to fractional distillation and a number of other processes, which result in different types of fuels, base oils, paraffin, asphalt and even some secondary products.