Abstract: A method for extraction of oil from oil shale in which the shale is first crushed and then classified by a rotating trammel screen into four separate portions of differing longest particle dimension, namely less than 1/4 inch, less than 1/2 inch, less than 3/4 inch and greater than 3/4 inch, with the first three portions being treated while passing through the trammel screen and each portion then separately centrifuged under conditions of centrifuge speed, time and added heat optimal for shale particles of that size. The fourth portion is recrushed. The applied heat may be dry heat, dry steam or wet steam, and the temperature range lies between 200 degrees Farenheit and the flash point of the oil to be reextracted from the shale. Pressures ranging from atmospheric to slightly above atmospheric may be applied.