Most of what you own crossed an ocean burning a fuel that will not pour at room temperature. Heavy fuel oil, sold as bunker C or IFO 380, is the residue left after a refinery has stripped out petrol, kerosene and diesel. At 20°C it behaves closer to cold asphalt than to a liquid, and pour points run as high as 30°C, so an unheated tank sets into a waxy, asphaltene-rich solid. What that forces on the ship: - Viscosity is specified at 380 centistokes at 50°C. Water sits near 1 cSt, and injectors need 10 to 15 cSt to atomise cleanly - Bunker tanks are steam-traced to roughly 40-50°C simply to be pumpable, then trimmed to 120-150°C at the final heater before injection - Density reaches 991 kg/m³, dense enough to sink in seawater, so a heavy fuel spill sludges the seabed rather than floating for skimming - Lower heating value sits near 40 MJ/kg against 42.7 for marine gas oil, yet the density advantage puts it ahead volumetrically at close to 40 GJ/m³ The reason shipping tolerates all o...