To reduce the viscosity of a fuel oil, what must be done?

Increasing the temperature of fuel oil is an effective method for reducing its viscosity. Viscosity refers to a fluid's resistance to flow; as temperature rises, the mobility of the fuel oil molecules increases, allowing them to move more freely. This process effectively reduces the thickness or stickiness of the oil, making it easier to pump and burn in combustion processes.

Higher temperatures provide the necessary energy for the oil molecules to overcome intermolecular forces, thus flowing more readily. It's essential to maintain a proper balance, as excessive temperatures could lead to combustion instability or damaging thermal degradation of the oil. This is why applying heat in a controlled manner is a common practice in managing fuel oil properties in various industrial applications.

In contrast, decreasing pressure, increasing the viscosity index, or switching to a different fuel does not directly address the viscosity in the same effective manner as increasing temperature. While pressure adjustments can have an impact on certain fluid characteristics, they are not the primary method for altering viscosity in fuel oils.