Synthetic oil is general better than mineral oil. However "Synthetic oil is always better" is not always correct for every circumstances. Quality of lubricating oil (finished product) depends on not only base oil but also additives, technologies, and know-how of each Manufacturer.

Selecting lubricating oil should not be "the highest quality", it should be "the most appropriate"

Below are characteristic of some common types of synthetic base oils:

Polyalphaolefins (PAOs)

PAOs, usually called synthetic hydocarbons, are the most common type of synthetic base oil used nowadays. PAOs oil provides excellent performance but its price is moderately high and has few limitations.

PAO base oil derived from crude oil, natural gas. PAO is made by synthesizing processing: polymerizing an alpha-olefin. By synthesizing process, PAO molecules are the same shape and size and are completely saturated. As the result, compare to mineral oil, PAO has higher viscosity index, improved oxidative and thermal stability, excellent demulsibility, hydrolytic stability, low pour point, low volatility, excellent low- and high-temperature performance.

Viscosity index of: PAO: 142-152; mineral oil group I, II: 80-120; mineral oil group III: 120-140

The negative characteristics of PAOs are the price and poor solubility. Poor solubility creates problem of choosing additives, dissolving additives.

Polyalkaline glycols (PAGs or PGs)

PAG base oils have several unique properties that allow them to work very well in certain applications. In general, they have excellent oxidative and thermal stability, very high VI, excellent film strength and an extremely low tendency to leave deposits on machine surfaces.

The negatives of PAGs are their very high cos.

Dibasic Acid Ester (Diester)

The properties of diester are somewhat similar to that of PGs. It has excellent oxidative and thermal stability, very high VI and excellent solubility, usued as an additive for PAO basestocks.

The negative characteristics of diester are the high cost and poor hydrolytic stability.

Polyol Ester

Polyol Ester have several excellent performance properties, including thermal stability, supper high VI and fire resistance. The most common application for polyol ester are fire-resistant hydraulic fuids, compressor, and jet engine oils.

The negative characteristics are, the same as Diester, high cost and poor hydrolytic stability.

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5 Base oil groups: classification and characteristics