Broadly speaking fuel oil is any liquid petroleum product that is burned in a furnace or boiler for the generation of heat or used in an engine for the generation of power , except oils having a flash point of approximately 40 ° C ( 104 ° F ) and oils burned in cotton or wool-wick burners .
Broadly speaking , fuel oil is any liquid petroleum product that is burned in a furnace or boiler for the generation of heat or used in an engine for the generation of power , except oils having a flash point of approximately +40 ° C and oils burned in cotton or wool-wick burners .