Experience in the industrial operation of boiler units and gas turbines, which run on heavy fuel oil, shows that the available research on the composition of the ash residue contained in heavy fuel oil, on the effect of separate components on the melting point of the ash, and the residue's ability to form deposits and cause corrosion of materials, does not make it possible to unequivocally judge the effect of various factors on the process of formation of deposits and the intensity of corrosion. Analysis of the data available in the literature shows that, at present, the regularity of behavior of the elements of the ash residue in a gas flow, and particularly the dependence of the properties of the ash residue on the operating conditions of the combustion chamber, have been studied to an insufficiently complete extent. It is well-known that vanadium is one of the most active elements of ash residue, insofar as corrosion and deposits are concerned. Therefore, only the behavior of vanadium is examined in the present study. This report established that there exists a quite definite dependence between the conditions in the combustion zone, the degree of completion of the burn-up process of the fuel particles, and the composition of the ash residue: the more completely the fuel burned in the zone of high temperature, the less vanadium in the ash residue and the less danger of the formation of deposits and the appearance of high-temperature (vanadium) corrosion.