Base oil is produced by means of refining crude oil. This means that crude oil is heated in order that various distillates can be separated from one another. Whether or not a crude oil is suitable to be made into a base oil is determined by the concentration of base oil molecules as well as how easily these can be extracted. There are large numbers of crude oils all around the world that are used to produce base oils. The most common one is a type of paraffinic crude oil, although there are also naphthenic crude oils that create products with better solubility and very good properties at low temperatures.