The process by which undesirable ingredients of different origins are removed from crude oil, in order to preserve the quality and characteristics of the oil, is called oil refining. Various methods of refining oil, besides affecting the quality of the product itself , also increase its utilization and thereby the economy value of the obtained oil. Other then undesirable, partially are also removed some of the valuable components of the crude oil, such as vitamins, proteins, antioxidants, phospholipids, sterols and others . Because of the loss of desirable components, oil refining process is contucted in shorter time period, at lower temperatures and high vacuum.