Not all synthetic oils are equal Some give better protection and last longer than others, depending on whether they're formulated with Ester or PolyAlphaOlefin (PAO) stock. Synthetic oils made from the ester class are much more expensive, but are more durable and hold up under hotter temperatures.
Synthetic oils have different base stocks, which comprise some 90% of the oil. The base stock is the actual lubricant The other 10% or so is the additive package. The relative ability of oils to lubricate is determined by the components of the base stock. There are two principal classes of base stocks used in real synthetic oils: synthesized hydrocarbons (PAOs) and organic esters.
The base stock materials used today many popular synthetic oils are made of carbon and hydrogen molecules. These
are synthesized from ethylene gas molecules into PolyAlphaOleflns (PAO). Almost all the synthetic oils sold in the stores are made with PAO base stocks. PAOs provide better viscosity characteristics, are more resistant to oxidation and have much better low operating properties than petroleum oils. PAOs are cheaper synthetic oil base stocks, and aren't as durable as the ester class of synthetic oils. Some of the popular brands of PAO oils include Amsoil and Mobil-1.
These are known as a Group IV oil.
Organic esters are made by reacting certain acids with alcohols, forming acid esters. There are alcohol diesters and
Polyol esters. This process uses expensive materials and results in lubricants that cost many times more than PAOs. Only esters are durable enough to withstand the rigors of jet engine operation and they are used in racing and high performance cars. These oils can cost $8 dollars or more a quart. Redline is an example of an ester synthetic oil. These are known as a Group V oil.