<P> Chemical substances--additives--are added to the base oil in order to meet the quality requirements for the end products in terms of, for example, friction and cleaning properties . Certain types of motor oils contain more than twenty percent additives . </P> <P> According to the American Petroleum Institute (API), base oils fall into five main groups . This breakdown is based on the refining method and the base oil's properties in terms of, among other things, viscosity and the proportion of saturates and sulfur content . </P> <P> The least refined type which produced by Solvent Refining . It usually consists of conventional petroleum base oils . </P> <P> API defines group I as "base stocks contain less than 90 percent saturates and / or greater than 0.03 percent sulfur and have a viscosity index greater than or equal to 80 and less than 120". </P>

Solvent extraction method of refining is adopted for which group of baseoil