you'll have to pull it out of mine before you can put in yours
just pulled from wikipedia, hope it explains something:
Synthetic Base Stocks
Synthetic motor oils have been made from the following classes of lubricants:
* Polyalphaolefin (PAO) = American Petroleum Institute (API) Group IV base oil
* Synthetic esters, etc = API Group V base oils (non-PAO synthetics, including diesters, polyolesters, alklylated napthlenes, alkyklated benzenes, etc.)
* Hydrocracked/Hydroisomerized = API Group III base oils. Chevron, Shell, and other petrochemical companies developed processes involving catalytic conversion of feed stocks under pressure in the presence of hydrogen into high quality mineral lubricating oil. In 2005 production of GTL (Gas-to-liquid) Group III base stocks began. The best of these perform much like polyalphaolefin. Group III base stocks are considered synthetic motor oil in North America.[2]