Primarily derived from the residual fractions of crude oil after the distillation process, these products — commonly referred to as furnace oils — play a vital role in both residential and industrial energy use. They are typically heavier and more viscous than lighter petroleum products such as naphtha and gasoline, making them ideal for heating, power generation, and certain types of vehicle applications. The classification and specifications of these oils can vary from one country to another, depending on national standards and regulatory frameworks. Their versatility and energy density make them a crucial component in many commercial and domestic operations worldwide.