Fuel oil is dense and viscous, so it is heated and cleaned on board before it burns. Gas oil flows more freely and normally needs no heating. Most ships run on one of these two groups, and the sulphur limit in force largely decides which one is used.
How Fuel Oil and Gas Oil Differ
| Fuel oil | Gas oil | |
|---|---|---|
| Production | Distillation residue and blend components | Middle distillate |
| Market names | VLSFO, HSFO, ULSFO, IFO 380 | MGO, LSMGO |
| ISO 8217 categories | RMA, RME, RMG, RMK | DMX, DMA, DMZ, DMB |
| Viscosity measured | At 50 °C, up to 380 mm²/s for RMG 380 | At 40 °C, 2 to 6 mm²/s for DMA |
| Treatment on board | Heating, settling and separators | No heating; cold flow and low viscosity need watching |
| Lower calorific value | 40.5 MJ/kg | 42.7 MJ/kg |
| Main use | Open sea voyages (VLSFO), ships with scrubbers (HSFO) | Emission control areas, port stays, small vessels |
Calorific values are the default figures in the EU FuelEU Maritime Regulation.
Types of Fuel Oil
VLSFO
Fuel oil with no more than 0.50% sulphur. Since the global limit took effect on 1 January 2020 it has been the main fuel outside emission control areas. Quality can vary between parcels, so a new stem goes into a separate tank and compatibility is checked.
HSFO
Fuel oil above 0.50% sulphur. It can only be used on ships with an exhaust gas cleaning system, or scrubber. It is graded by viscosity, such as 180, 380, 500 and 700.
ULSFO
Fuel oil with no more than 0.10% sulphur. It can replace gas oil inside an emission control area and uses the ship's existing fuel oil line. Availability varies by port.
Types of Gas Oil
Marine gas oil (MGO) is a distillate fuel burned in ship engines. The market name MGO usually means the DMA or DMZ category of ISO 8217. LSMGO is a trade name for MGO with no more than 0.10% sulphur and is not a separate ISO category. MDO generally corresponds to DMB and may contain some heavier material. Gas oil containing biofuel is classed as DFA, DFZ or DFB.
Gas oil is used in the 0.10% sulphur areas of the Baltic, the North Sea, North America, the US Caribbean and, since 1 May 2025, the Mediterranean. The Sea of Marmara and the Turkish Straits lie outside that area, but Türkiye's national regulation applies 0.1% to ships at berth and to ships anchored for more than two hours.
Orders and Offers
Bunkerist supplies vessels with fuel oil (including VLSFO) and gas oil (MGO). For an offer we need the vessel name, IMO number, port, ETA, product and quantity. Stating the category and sulphur together avoids confusion, for example "RMG 380, max 0.50% S" or "DMA, max 0.10% S".
Send the details to info@bunkerist.com or call +90 216 455 44 40. How we work is on our Bunker Trading page and the ports we work in are on our Ports page.