3.7 Maritime fuel classification
In the maritime field, another type of classification is used for fuel oils:
- MGO (Marine Gasoil)- Roughly equivalent to no. 2 fuel oil, made from distillate only
- MDO (Marine Diesel Oil) - Roughly equivalent to no. 3 fuel oil, a blend of heavy gasoil that may contain very small amounts of black refinery feed stocks, but has a low viscosity up to 12 cSt, so it needs not be heated for use in internal combustion engines
- IFO (Intermediate Fuel Oil) - Roughly equivalent no. 4 fuel oil, a blend of gasoil and heavy fuel oil, with less gasoil than marine diesel oil
- HFO (Heavy Fuel Oil) - Pure or nearly pure residual oil, roughly equivalent to no. 5 and no. 6 fuel oil
- NSFO (Navy Special Fuel Oil) - Another name for no. 5 HFO
- MFO (Marine Fuel Oil) - Another name for no. 6 HFO
Marine diesel oil contains some heavy fuel oil, unlike regular diesels.
Standards and classification
CCAI and CII are two indexes which describe the ignition quality of residual fuel oil, and CCAI is especially often calculated for marine fuels. Despite this, marine fuels are still quoted on the international bunker markets with their maximum viscosity (which is set by the ISO 8217 standard - see below) due to the fact that marine engines are designed to use different viscosities of fuel. The unit of viscosity used is the centistoke (cSt) and the fuels most frequently quoted are listed below in order of cost, the least expensive first.
- IFO 380 - Intermediate Fuel Oil with a maximum viscosity of 380 centistokes (<3.5% sulfur)
- IFO 180 - Intermediate Fuel Oil with a maximum viscosity of 180 centistokes (<3.5% sulfur)
- LS 380 -Low Sulphur (<1.0%) intermediate fuel oil with a maximum viscosity of 380 centistokes
- LS 180 - Low Sulphur (<1.0%) intermediate fuel oil with a maximum viscosity of 180 centistokes
- MDO - Marine Diesel Oil
- MGO - Marine Gasoil
- LSMGO - Low-sulphur (<0.1%) Marine Gasoil - The fuel is to be used in EU Ports and Anchorages. EU Sulphur directive 2005/33/EC
- ULSMGO -Ultra Low Sulfur Marine Gasoil - referred to as Ultra Low Sulphur Diesel (sulphur 0.0015% max) in the US and Auto Gasoil (sulphur 0.001% max) in the EU. Maximum sulphur content allowable in US territories and territorial waters (inland, marine, and automotive) and in the EU for inland use.
The density is also an important parameter for fuel oils since marine fuels are purified before use to remove water and dirt from the oil. Since the purifiers use centrifugal force, the oil must have a density which is sufficiently different from water. Older purifiers work with a fuel having a maximum of 991 kg/m3; with modern purifiers, it is also possible to purify oil with a density of 1010 kg/m3. The first British standard for fuel oil came in 1982. The latest standard is ISO 8217 issued in 2017. The ISO standard describes four qualities of distillate fuels and 10 qualities of residual fuels. Over the years, the standards have become stricter on environmentally important parameters such as sulphur content. The latest standard also banned the adding of Used Lubricating Oil (ULO).ph