Marine Fuel Glossary: Bunkering Terms Explained
The bunkering vocabulary, defined in plain English.
Fuel grades
- VLSFO — very low sulphur fuel oil, 0.50% sulphur maximum.
- HSFO — high sulphur fuel oil, typically 3.5% sulphur.
- ULSFO — ultra low sulphur fuel oil, 0.10% sulphur.
- MGO — marine gas oil, a distillate fuel.
- LSMGO — low sulphur marine gas oil for emission control areas.
Delivery and operations
- Stem — a confirmed bunker order for a specific vessel, quantity and window.
- Barge — the vessel delivering fuel alongside the receiving ship.
- Ex-wharf — fuel taken directly at a berth rather than by barge.
- BDN — bunker delivery note, the legal record of the delivery.
- Mass flow meter — a metering system measuring delivered mass directly.
Quality terms
- Cat fines — abrasive catalyst particles that cause engine wear.
- Viscosity — flow resistance, determining required heating.
- Flash point — the minimum safe ignition temperature, regulated for marine fuels.
- Compatibility — whether two fuels can be mixed without sludge formation.
- Representative sample — a sample drawn continuously through the delivery.
Commercial terms
- Hi-5 spread — the price differential between VLSFO and HSFO.
- Delivered premium — the hub-specific mark-up over the cargo benchmark.
- Scrubber — exhaust gas cleaning system allowing HSFO use.
- Demurrage — compensation for delay beyond agreed laytime.
- Claim — a formal dispute over quantity or quality delivered.