TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Condition: The settling treatment is carried out at 5-25 degrees C for up to 48 hours. Prior to the first separation stage, the waste cooking oil is subjected to a straining step conducted at ambient temperature and employing a filter screen having a pore size of 200-600 mu m. The second separation stage is conducted using a filter having a pore diameter of 0.5-10, preferably 1-5 mu m. The oil fraction recovered from the first separation stage is warmed at 10-30 degrees C before passing to the second separation stage. EXAMPLE - Waste vegetable cooking oil was collected from commercial cooking and catering operations. The waste vegetable oil included rape seed oil, soya oil and sunflower oil in varying amounts. The waste oil was passed through a filter screen having a pore size of 400 mu m at an ambient temperature of 15 degrees C, to remove large solid particles and other matter. The thus filtered oil was introduced into a settling tank and allowed to stand, again at 15 degrees C and atmospheric pressure for 48 hours. Inspection of the contents of the settling tank after 48 hours revealed that the waste oil had separated into a clear oil fraction and a sludge fraction, beneath the oil fraction, containing solid and dense material settled from the oil fraction. A minimal amount of light solid matter had collected on the surface of the oil fraction. This was removed by gently skimming the top of the clear oil, after which the oil fraction was decanted from the settling tank using a pump, without disturbing the sludge fraction. The recovered oil fraction was passed through a heat exchanger and warmed by indirect heat exchange with hot water in a water jacket to 20 degrees C. The warmed oil fraction was passed by pumping through a filter assembly comprising a cylindrical filter screen having a pore size of 1 mu m. The filtrate was collected as a clear oil fraction. The oil fraction had improved performance as a fuel, and reduced environmental impact.