a method of extracting recovering oil from vegetable material in which oil bearing material is heated and subjected to sonication at least one frequency above 400 khz , removing a first yield of oil by decanting and subjecting the retained material to centrifugal separation to separate out a second yield of oil . preferably the raw vegetable material is passed through a screw press and the obtained material is heated and subjected to the ultrasonic treatment and then allowed to settle for a predetermined period before decanting the oil layer . preferably two frequencies above 400 khz are used , one below 1 mhz and the second from 1 mhz . there are many potential transducers arrangements possible for producing standing waves .