As fuel oil is heated, what happens to its viscosity?

As fuel oil is heated, its viscosity decreases. Viscosity is a measure of a fluid's resistance to flow, and for most liquids, including fuel oil, heating the liquid reduces its viscosity. This is because the increased temperature provides energy that allows the molecules within the fuel oil to move more freely, thereby decreasing the internal friction that restricts flow. Consequently, as viscosity decreases, the fuel oil flows more easily, which is essential for efficient combustion in a boiler system. This principle of the relationship between temperature and viscosity is important for boiler operators to understand, as it affects fuel delivery systems and combustion efficiency.