The base oil is said to be a lubricant as a lubricant base. The most important component of the lubricant from volumetric view is base oil and averaged over 95% of the lubricant's formulation. In some lubricants (compressor and hydraulic oils), 99% of the oil is the base oil, and only 1% of it is an additive. Base oils can be obtained from petroleum or non-oil sources. Most of the basic oil in the world comes from refining crude oil. The major components of the 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: Low oil, oil thickening, and sediment formation 

2. Surface activity: foaming, air release, emulsion formation and pressure 

3. Oxidation: formation of sediment, oil thickening, sludge formation and corrosion of metals 

4. Viscosity: low temperature fluidity, energy wasting, wear protection and proper cooling. 

5. Solubility: Engine cleanliness, seals compatibility, process applications and formulation stability. 

Base oil types 

In general, base oils are divided into  three  minerals, natural and synthetic categories. 

1. Base mineral oils: 

The base oil obtained from crude oil is called the mineral base oil, which itself consists of two groups of paraffinic and naphthenic oils derived from crude petroleum refining. Paraffinic oils are composed of normal hydrocarbons ( right chains) and iso-hydrocarbons (branched). But naphthenic oils are composed of one or more ringed hydrocarbons. Paraffinic oils have the following properties in comparison to naphthenic oils: 

Higher temperature 

Less specific gravity 

Higher viscosity index 

Less solubility 

High resistance to oxidation 

Low volatility and therefore a higher ignition point  

naphthenic oils are generally used for low temperature ranges and when low dropping points are needed. Specially used in hydraulic oils, coolants, rubber oils, metalworking and in cylinder lubricants for large engines and lubricants.  

2. Base oils 

Over the past two decades, due to increased environmental considerations, attention has been paid to natural lubricants. These oils come from plant sources. The main components of the natural oils are a mixture of triglycerides that contain acid-bound carboxylic acids with high chain lengths. These carboxylic acids are known as fatty acids. In general, straight chains have a length of 8 to 22 carbon atoms, which may be completely saturated, or have one or more unsaturated transplants on their chains. 

Vegetable oils can be used in their natural form for lubrication. The lubricating power of vegetable oils is much more than mineral oils. The combustion and ignition point of vegetable oils is much higher than mineral oils (about 326 ° C). But these oils, in the natural form, do not have enough oxidation stability. Another undesirable feature of vegetable oils is the high dropping point, which can be solved by adding appropriate additives.  

3.Synthetic base oils 

Synthetic or synthetic oils are oils that are synthesized or constructed by connecting one or more organic components of low molecular weight under controlled conditions. This combination, which is carried out under controlled physical and chemical conditions, makes the oil produce certain properties that were previously intended. This has led to the expansion of the use of synthetic oils that can withstand a significant amount of temperature and pressure without altering the structure and at the same time reduce the risk of fire. However, the use of synthetic oils is logical when: 

- The use of synthetic oils reduces operating costs so much that it can compensate for high purchasing costs. 

- The use of synthetic oils will solve the problem with the use of mineral oils. Like operating conditions at very high or very low temperatures.