A process for the treatment of waste oil comprises the steps of (a) supplying a stream of the waste oil to a dehydrator to dehydrate the waste oil and obtain a stream of dehydrated waste oil; (b) supplying the stream of dehydrated waste oil to a fractionated distillation column having a lower tray, an upper tray and a middle tray therebetween, wherein the lower tray is operated at a temperature of 370 to 390.degree. C. under a sub-atmospheric pressure of 50 to 100 mmHg, the middle tray is operated at a temperature of 265 to 280.degree. C. under a sub-atmospheric pressure of 35 to 45 mmHg and the upper tray is operated at a temperature of 100 to 110.degree. C. under a sub-atmospheric pressure of 30 to 40 mmHg; (c) withdrawing from the distillation column a bottom product comprising a bituminous material; (d) withdrawing a first side stream from the distillation column between the first and second trays, the first side stream comprising a heavy oil having a viscosity of 130 to 180 cSt at 40.degree. C.; (e) withdrawing a second side stream from the distillation column between the second and third trays, the second side stream comprising a light base oil having a viscosity of 38 to 43 cSt at 40.degree. C.; (f) withdrawing a third side stream from the distillation column above the third tray, the third side stream comprising diesel having a viscosity of 4 to 7 cSt at 40.degree. C.; (g) withdrawing from the distillation column an overhead product comprising naphtha; and (h) recovering the bituminous material, heavy oil, light base oil, diesel and naphtha. The process according to the invention enables one to produce refined oil which is substantially free of heavy metal contaminants.