Distillation separates each crude oil into fractions known as light naphtha, medium naphtha, heavy naphtha, light oil, heavy oil and residuum according to their boiling points. Light, medium and heavy naphthas have octane numbers of 90, 80 and 70 respectively. The fractions into which one barrel of each type of crude splits are given in the table:

	Light	Medium	Heavy	Light	Heavy
	naphtha	naphtha	naphtha	oil	oil	Residuum
Crude 1	0.1	0.2	0.2	0.12	0.2	0.13
Crude 2	0.15	0.25	0.18	0.08	0.19	0.12

N.B. There is a small amount of wastage in distillation.