Heating oil
Heating oil means petroleum that is No. 1, No. 2, No. 4light, No. 4heavy, No. 5light, No. 5heavy, and No. 6 technical grades of fuel oil; other residual fuel oils (including Navy Special Fuel Oil and Bunker C); and other fuels when used as substitutes for one of these fuel oils. Heating oil is typically used in the operation of heating equipment, boilers, or furnaces.