Another source of lubricant base fluids is the synthetic route. Traditionally, synthetics was defined as “A product prepared by chemical reaction of lower molecular weight materials to produce a fluid of higher molecular weight designed to provide certain predictable properties.” Currently, there are two types of synthetic base oils commercially available.(PAO and hydrocracked base oil) Until mid 1990, Polyalphaolefins(PAO) were the most widely used conventional synthetic lube base fluid in the US and Europe. They are made by combining two or more decent molecules into an oligomer, or short chain length polymer. Because PAOs are all-hydrocarbon structures and wax-free, they have low pour points, usually below -40°C, very high viscosity indexes and good thermal stability. But because of limited availability of raw material, PAO production was limited to very specific application. However, since mid 1990s, new type of synthetic base oil, hydrocracked VHVI(very high viscosity index) base stocks like S-OIL's Ultra-S, have come to use because of commercial availability. Because VHVI base oil is made by chemically converting the petroleum based molecules into a PAO-like molecular structure, it shows quite similar properties to PAO at much less cost. Hence S-OIL’s Ultra-S series will make an excellent economical alternative for PAOs for applications like crankcase engine oils, gear and power train lubricants and some industrial lubricants requiring very high quality standard and extended life.