FUEL OIL also called furnace oil, fuel consists mainly of residues from crude-oil distillation. It is used primarily for steam boilers in power plants, aboard ships, and in industrial plants. Commercial FUEL OILs usually are blended with other petroleum fractions to produce the desired viscosity and flash point.
Furnace oil consists largely of residues from crude oil refining. These are blended with other suitable gas oil fractions in order to achieve the viscosity required for convenient handling. As a residue product, fuel oil is the only refined product of significant quantity that commands a market price lower than the cost of crude oil.