Base oil is an oil that is considered as a base for lubricants. The most important component of lubricants in terms of volume is base oil, and it makes up more than 95% of the formulation of a lubricant in terms of weight. In some lubricants (compressor and hydraulic oil), 99% of the oil is the base oil and only 1% is made up of additives. Base oils can be obtained from petroleum or non-petroleum sources. Most of the base oils used in the world are obtained from crude oil refining. The main components of base oils are paraffinic, naphthenic and aromatic compounds.

Chemical properties of base oil and how it affects the performance of the final lubricant

1- Volatility: reduction of oil, thickening of oil and formation of sediments

2- Surface activity: foaming, air release, emulsion formation and compressibility

3- Oxidation: formation of sediments, thickening of oil, formation of sludge and corrosion of metals

4- Viscosity: fluidity at low temperature, energy loss, protection against wear and proper cooling

5- Solving power: engine cleanliness, compatibility with sealants, process applications and formulation stability

The base oil obtained from crude oil is called mineral base oil, which includes two categories of paraffinic and naphthenic oils, which are obtained from raw crude oil. Paraffinic oils consist of normal hydrocarbons (straight chain) and iso hydrocarbons (branched). But naphthenic oils are composed of one or more saturated cyclic hydrocarbons. Paraffinic oils have the following properties compared to naphthic oils:

Higher melting temperature

    Less specific weight

    Higher viscosity index

    Less solvent

    High resistance to oxidation

    Low volatility and as a result higher flash point

Naphthenic oils are generally used for low temperature ranges and when a low pour point is required. They can be used especially in hydraulic oils, coolants, rubber production oils, metalworking and in cylinder lubricants for large engines and greases.