Represent the predominant component in the majority of lubricants. The finished product may contain from 70% to 99% base oil. The quality of base oils is closely linked to the type of crude oil and the process used. The base oils can be of different natures:

Minerals: mix of hydrocarbons obtained from crude by a conventional refinery process or by a standard hydrogenation process. Products of a different viscosity within the distilling process are called “cuts”.

The number of “cuts” and relative viscosity properties depend on the manufacturer and type of process. The following oils are normally produced:

• a very fluid stock (SN 80 ÷ 100 or spindle)

• a fluid stock (SN 125 ÷ 170 typically 150)

• a medium stock (SN 350 ÷ 600)

• a BrightStock (BS 150 ÷ 200)