Synthetic oils

 

Summary
Synthetic oils offer better protection against engine wear and can operate at higher temperatures. They have better low temperature viscosity, are chemically more stable and allow for closer tolerances in engine components without loss of lubrication.

Synthetic lubricating oils are more costly to manufacture and to use but they have a number of advantages over conventional mineral oils.
They offer better protection against engine wear and can operate at the higher temperatures needed by performance engines; they have better low temperature viscosity, without the wax impurities that coagulate at low temperatures; they are chemically more stable; and they are generally thinner, so they allow for closer tolerances in engine components without loss of lubrication. They also last considerably longer, extending oil change intervals out to 15,000 Kms or 10,000 miles or more, which benefits the environment by reducing the used oil stream.
True synthetic oils are based on man-made hydrocarbons, commonly polyalphaolefin or PAO, but very few of the synthetic oils on the market are full PAO oils. Many of the oils allowed to be labeled as synthetic are in fact blends of processed mineral oil and PAO, or even just heavily processed natural crude oil.
The American Petroleum Institute, or API, classifies oils into five groups.
Group 1 oils are produced by simple distillation of crude oil, which separates the components of the oil by their boiling point, and by the use of solvents to extract sulfur, nitrogen, and oxygen compounds. This was the only commercial refinement process until the early 1970s, and the bulk of commercial oil products on the market are still produced by this process.
Group 2 and Group 3 oils are refined with hydrogen at much higher temperatures and pressures, in a process known as hydro-cracking. This process results in a base mineral oil with many of the higher performance characteristics of synthetic oils, and the more heavily hydro-cracked Group 3 oils have a very high viscosity index - above 120 - making them the equivalent of PAO synthetic oils.
Group 4 oils are all of the synthetic polyalphaolefins, the PAO group, and Group 5 includes all other types of synthetic oil.
Over time, lubricating oil breaks down by reacting with dissolved atmospheric oxygen. By hydrogenating the oil in a hydrocracker refinery, and with the use of oxidation-inhibiting additives, this deterioration-rate can be slowed by more than a hundredfold. Hydroprocessing also reduces the presence of aromatic hydrocarbons, which gives more effective oxidation inhibitor action, minimizes sludge and varnish deposits, and generally avoids other related machinery problems.