Furnace oil in the current marketing range meets Bureau of Indian Standards Specification IS : 1593 - 1982 for fuel oils, gradeViscosity:Viscosity is the most important characteristic in the furnace oil specification. It influences the degree of pre-heat required for handling, storage and satisfactory atomization. If the oil is too viscous it may become difficult to pump, burner may be hard to light and operation may be erratic. Poor atomization may result in the carbon deposits on the burner tips or on the walls. The upper viscosity limit for furnace oil is such that it can be handled without heating in the storage tank is excepting under server cold conditions. Pre-heating is necessary for proper atomization.