Abstract: In a method and installation for providing a stable mixture of heavy oil and water to an oil burner, heavy oil is supplied from a storage tank to an oil tank where it is maintained at a selected pressure and a temperature of 35.degree.-45.degree. C. Water is supplied from a water source to a water tank where it is maintained at a selected pressure and a temperature of 30.degree.-40.degree. C. Oil from the oil tank and water from the water tank are pumped into and through an agitator at a pressure of 3.5-5.5 kg/cm.sup.2 while maintaining the temperature of the oil and water above 30.degree. C. The agitator comprises a cylindrical casing containing a first set of static disc-like elements having inclined holes to produce a swirling motion of the oil-water and a second set of static disc-like elements each having a central protruding dome portion surrounded by a rim portion.