Abstract: An oil burner system includes a burner nozzle connected to a supply of fuel oil by a nozzle assembly having integrated therein an electric heater for prewarming the oil fed to the nozzle. The nozzle assembly has first connector at one end directly connected to the burner nozzle and a second connector at its other end directly connected to an oil supply conduit. The preheater comprises an elongated rectangular PTC heating resistor having a pair of parallel sides of greater width than the thickness of the resistor and coextensive electrical contacts extending longitudinally and transversely in electrical engagement with the parallel sides. A pair of parallel flattened thin wall metal conduit sections extend coextensively between the first and second connectors and define thin unimpeded generally rectangular cross section flow path for the oil to be heated.