A refining process used to separate components (unsaturated hydrocarbons) from lube distillates in order to enhance the oil's oxidation stability, viscosity index, and response to additives. The oil and the solvent extraction media are mixed in an extraction tower, concluding in the formation of two phases: a heavy phase consisting of the undesirable unsaturates dissolved in the solvent, and a lighter phase made of a high quality oil with some solvent dissolved in it. The phases are separated and the solvent regained from each through distillation.
