Abstract: A method of treating a material to recover an oil from the material comprises heating the material to evaporate the oil, removing gas phase fluids from the material, and separating the oil from the gas phase fluids removed from the material, wherein the method includes mixing hot vapour with the material. The material being treated in the chamber is heated by friction within the chamber generated by a rotating shaft and flail. Injection of hot vapour improves the efficiency of the process to separate oil and any other evaporable liquids at lower temperatures. The thermal energy generated within the chamber is not consumed in changing the phase of large quantities of liquids in the material, and more of the energy generated is available to heat up the material and evaporate the oil fractions from the solids.