Oil burner

An oil burner comprising, a pressure atomizing nozzle having a swirl chamber and rated for usual flow rates of 0.4 to 0.85 gallons per hour, a pressure supply of light fuel oil having a viscosity of about 12 centistoke at 20.degree. C., and lower connected to said atomizing nozzle swirl chamber, a flow heater connected to said atomizing nozzle upstream of said swirl chamber for preheating the fuel oil to a temperature of up to 150.degree. C. and below a coking and cracking temperature of the light fuel oil, said flow heater comprising a cylindrical heating element having a cylindrical outer surface, an oil feeding pipe surrounding said cylindrical heating element, a fitting connected to said atomizing nozzle, said oil feeding pipe connected to said fitting, a block of good heat conducting material pressing against the outer surface of said cylindrical heating element and said fitting for establishing a thermal connection therebetween, said oil feeding pipe defined in the form of a helical recess at the interface of said block and said heating element, said cylindrical heating element being shink fitted into a bore of said block, whereby said atomizing nozzle can burn light fuel oil at lower flow rates than that for which it is rated.