Marine fuel grades, explained
Which fuel can you burn, where? A plain-English guide to grades and sulphur limits.
Marine fuels fall into two families defined by the international standard ISO 8217: light distillates (DM grades) and heavier residual fuels (RM grades). Which one you can burn depends mainly on its sulphur content and where the ship is.
| Grade | Type | Max. sulphur | Typically used |
|---|---|---|---|
| MGO / LSMGO ISO 8217 DMA, DMZ | Distillate | 0.10% | In Emission Control Areas and at berth in EU ports; auxiliary engines; smaller vessels |
| MDO ISO 8217 DMB | Distillate (may contain some residual) | depends on the product | Smaller engines and some coastal trades |
| ULSFO ISO 8217 RM grades | Residual | 0.10% | In ECAs, as an alternative to gasoil for engines designed for residual fuel |
| VLSFO ISO 8217 RM grades | Residual | 0.50% | The main fuel worldwide outside ECAs since IMO 2020 |
| HSFO (e.g. RMG 380) ISO 8217 RM grades | Residual | above 0.50% | Only with an approved scrubber (EGCS), outside areas that restrict scrubber use |
Sulphur limits at a glance
- Worldwide: 0.50% since 1 January 2020 (MARPOL Annex VI, "IMO 2020").
- Emission Control Areas: 0.10% in the North Sea and English Channel, the Baltic, North American and US Caribbean areas, and the Mediterranean since 1 May 2025.
- EU ports: 0.10% for ships at berth for more than two hours.
- Scrubbers can be used instead of low-sulphur fuel where allowed, but some ports and countries restrict open-loop washwater discharge.
Reading a residual grade name
In a name like RMG 380, "RM" means residual marine, the letter is the specification category, and the number is the maximum viscosity in centistokes (cSt) at 50°C. Higher viscosity fuels need more heating before they can be pumped and injected.
Beyond sulphur: the next rules
Since 2024 ships calling at EU ports are covered by the EU Emissions Trading System, and since 2025 by FuelEU Maritime, which limits the greenhouse gas intensity of the energy used on board. This is pushing demand for biofuel blends, LNG and, in time, methanol and ammonia. We follow these developments closely and can advise on availability port by port.
Compatibility and quality
Different batches of residual fuel, particularly VLSFOs, are not always compatible with each other. Avoid mixing new fuel with what is already on board where possible, check the Certificate of Quality before delivery, and keep the MARPOL sample. If something goes wrong, we help you with the claim.
This guide is a general overview, not legal advice. Rules change and vary by country and port: always check the regulations that apply to your voyage, or ask us.
Not sure which grade to order?
Tell us the vessel, route and engines: we'll advise on the right grade and the best place to buy it.