the biggest issue is that the oil needs to not only be very hot to allow ignition with a spark, and then with a pressured system the delivery needs to be very accurately metered, you would need to have a tank with the oil at about 90 degrees c and then a nozzle heater to bring it up to somwhere in the region of 220 degrees c i belive, waste oil doesnt need such high temps, needs more like 150 degrees c,