The invention provides methods for treating a source oil phase consisting of heavy oil, bitumen, a mixture of heavy oil and bitumen, a mixture of solvent and heavy oil or bitumen or both. The method comprises: introducing the source oil phase to a heated lower section of a device to provide an interior source oil phase; heating the interior source oil phase so as to thermally separate a light oil phase component therefrom and provide a vaporized light oil; and condensing the vaporized light oil phase on one or more internal cooling fins housed within the upper section of the device, to provide a condensed light oil phase liquid, wherein the internal cooling fins are angled so as to direct the condensed light oil phase liquid downwardly to a light end collection system.