Heavy fuel oil (HFO)

Heavy fuel oil (HFO) is the residual marine fuel left after distillation and cracking of crude oil, blended with cutter stock to a target viscosity, the standard grades being RMG 380 and RMK 500 under ISO 8217. It is highly viscous and must be heated to about 130 to 150 degrees C for pumping and injection, carries asphaltenes, vanadium, and sulfur, and traditionally ran up to 3.5% sulfur before the MARPOL Annex VI 0.50% global cap (0.10% in ECAs) from January 2020. Use now needs either a compliant low-sulfur blend or an exhaust-gas scrubber.