Black-oil tanker (HFO)

A black-oil tanker carries dirty or black petroleum products: heavy fuel oil, fuel oil, crude, and residual cargoes, as opposed to clean white products like gasoline and gas oil. The term black oil names the cargo grade, not a fixed size class, and applies across MR, LR, and larger hulls trading in the dirty market. Cargo tanks are heated by steam or thermal-oil coils because heavy fuel oil and residuals are too viscous to pump at ambient temperature. The dirty product trade moves fuel oil and residuals from refineries to power stations, bunker hubs, and blending terminals, and many of these ships also lift crude when the market favors it.