It is also known as synthetic base oils and is the best grade of petroleum base oil, since they are fully produced by Hyrocracking, which make these oils purer.
Consists of synthetic oils made of Poly-alpha-olfiens PAO. Poly-alpha-olfiens PAO oils are much more stable in extreme temperatures, which make much more suitable for use in very cold weather (as found in northern Europe) as well as very hot weather (as in Middle East).
Any type of base oil other than mentioned in the previously defined groups. They include, among others, naphthenic oils and esters