Short answer: marine gas oil (MGO) is a pure distillate fuel, specified as ISO 8217 grade DMA or DMZ. Commercial vessels use it in auxiliary engines and boilers, for fuel changeover before emission control areas, and as the main fuel on many smaller vessels. When supplied with no more than 0.10% sulphur it is called low sulphur MGO (LSMGO).
What makes MGO different
MGO contains no residual components. It is clear and bright, has a low viscosity (2 to 6 mm²/s at 40°C for DMA) and does not need heating. That makes it simple to handle, but its low viscosity and lower natural lubricity bring their own considerations.
Where commercial vessels use MGO
- Auxiliary engines and generators on deep-sea vessels that keep residual fuel for the main engine.
- Boilers and other equipment that run more reliably on distillate.
- Emission control areas, where 0.10% sulphur fuel is required.
- EU ports at berth, where 0.10% sulphur fuel is required.
- Offshore, harbour and coastal vessels that run entirely on distillate.
- Engine start-up and manoeuvring on some vessels.
DMA, DMZ and DMB
DMA and DMZ are the MGO grades. DMZ has a higher minimum viscosity, which helps engines whose fuel pumps need more viscosity at operating temperature. DMB is marine diesel oil (MDO), which allows higher viscosity and density and may contain traces of residual fuel. See marine diesel oil for the comparison.
Operational points for engineers
Minimum viscosity
Engine makers specify a minimum viscosity at the fuel pump, commonly around 2 to 3 cSt. In a hot engine room, MGO can fall below it. Fuel coolers or chillers keep viscosity in range.
Changeover
Switching from hot residual fuel to MGO too fast can cause thermal shock and fuel pump sticking. Follow a controlled changeover procedure and record it as MARPOL requires when entering an ECA.
Lubricity
Desulphurisation reduces natural lubricity. ISO 8217 limits the wear scar to 520 µm, but low-lubricity fuel can still increase pump wear.
Cold flow and storage
Check cloud point and cold filter plugging point for cold-water routes. Keep tanks clean and drain water, particularly if the fuel contains FAME, which supports microbial growth.
Buying MGO
- State the grade (DMA or DMZ), the sulphur limit and the ISO 8217 edition.
- State whether FAME content is acceptable under ISO 8217:2024.
- Check for small-quantity charges on low volumes.
- Combine MGO with your residual stem where the supplier can deliver both.
See MGO supply in Singapore and LSMGO.
Frequently asked questions
Why do ships need MGO if they burn VLSFO?
MGO is used for auxiliary engines, boilers, ECA compliance at 0.10% sulphur and fuel changeover. Many ships carry both residual fuel and MGO.
What is the sulphur content of marine gas oil?
It depends on the grade ordered. ISO 8217 allows up to 1.00% for DMA, but statutory limits apply: 0.50% outside ECAs and 0.10% inside them. LSMGO is supplied at 0.10% or less.