Abstract: An oil tool and method for controlling the accumulation of paraffin and deposits in downhole oil string and oil transmission flow lines is provided by employing at various locations in the downhole oil string or in the oil transmission flow lines a coupling device with an inside liner of a non magnetic material surrounded by a magnet and shield of a magnetic material. The preferred application employs at least two magnets having their north pole and south pole aligned in opposite directions held in place in relation to a magnetic outer shield or casing by a non magnetic restraining ring.