The main reason of combustion problems in liquid fuels, especially in number 6 fuel oil, is the high viscosity of the fluid. In order to resolve the problems of first ignition, pulverization and combustion, viscosity is lowered by means of main tank serpentines, heat exchangers, daily heating of drum and electrical heaters in burners. Batch combustion and foaming of fuel are caused by excess heating with stream and electrical heaters. However, it is known that the reduction of viscosity with additives is not only more economical but also increases the combustion efficiency, reduces the emission, prevents corrosion and fuel polymerization. In this study, the reduction of the viscosity of the heavy fuel oil with temperature and additive ratio and meanwhile, the improvement of the pulverization and the lowering of the ignition point due to this viscosity reduction were investigated. According to the models that are formed in accordance with Arrhenius equation, while the viscosity of the pure fuel oil varies as mu = -19,1e([-8686, 2/T]) depending on the temperature, these values were found as mu = -18, 7e([-7946, 6/T]), mu = -18,5e([-7852, 4/T]) ve mu = -18, 4e([-7816, 9/T]) depending on the additive concentration increment and temperature. While the constants A and B in Arrhenius equation were -19,1 and -8086,2 for number 6 fuel oil, it was determined that when the concentration of the manganese additive in fuel oil was raised to %0,5, the constants A and B were also raised to -18,4 and -7816,9, respectively.