Marine Fuel (ISO 8217)

In the maritime industry the following type of classification is used for marine fuel oils:

  • MGO (Marine gas oil) – roughly equivalent to No. 2 fuel oil, made from distillate only
  • MDO (Marine diesel 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/400 C so it need not be heated for use in internal combustion engines
  • IFO (Intermediate fuel oil) A blend of gasoil and heavy fuel oil, with less gasoil than marine diesel oil
  • MFO (Marine fuel oil) – same as HFO (just another “naming”)
  • HFO (Heavy fuel oil) – Pure or nearly pure residual oil, roughly equivalent to No. 6 fuel oil

Marine diesel oil contains some heavy fuel oil, unlike regular diesels. Also, marine fuel oils sometimes may contain waste products such as used motor oil.

Standards and classification

Marine fuels were traditionally classified after their kinematic viscosity. This is a mostly valid criteria for the quality of the oil as long as the oil is made only from atmospheric distillation. Today, almost all marine fuels are based on fractions from other more advanced refinery processes and the viscosity itself says little about the quality as fuel. CCAI and CII are two indices 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.[1]. The unit of viscosity used is the Centistoke 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/500 C
  • IFO 180 – Intermediate fuel oil with a maximum viscosity of 180 Centistokes/500 C
  • LS 380 – Low-sulphur (<1.5%) intermediate fuel oil with a maximum viscosity of 380 Centistokes/500 C
  • LS 180 – Low-sulphur (<1.5%) intermediate fuel oil with a maximum viscosity of 180 Centistokes/500 C
  • MDO – Marine diesel oil.
  • MGO – Marine gasoil.

The density is also an important parameter for fuel oils since marine fuels are cleaned by centrifugal type separators before use to remove water and dirt from the oil. Since the separators use centrifugal force, the oil must have a density which is sufficiently different from water. Conventional type separators of purifier type  have a maximum density limit of 991 kg/m3/150 C ; with modern High Density type separators it’s possible to clean fuel oils with a maximum density of 1010 kg/m3/150 C.

The first British standard for fuel oil came in 1982. The latest standard is ISO 8217 from 2005. The ISO standard describe 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 sulfur content. The latest standard also banned the adding of used lubricating oil (ULO).

ISO 8217 Fuel Standard Fourth Edition (source: DNV & ISO)


Parameter Unit Limit DMX DMA DMZ DMB
Viscosity at 40°C mm²/s Max 5.500 6.000 6.000 11.00
Viscosity at 40°C mm²/s Min 1.400 2.000 3.000 2.000
Micro Carbon Residue
at 10% Residue
% m/m Max 0.30 0.30 0.30
Density at 15°C kg/m3 Max 890.0 890.0 900.0
Micro Carbon Residue % m/m Max 0.30
Sulphur a % m/m Max 1.00 1.50 1.50 2.00
Water % V/V Max 0.30b
Total sediment by hot filtration % m/m Max 0.10b
Ash % m/m Max 0.010 0.010 0.010 0.010
Flash point 0°C Min 43.0 60.0 60.0 60.0
Pour point, Summer 0°C Max 0 0 0 6
Pour point, Winter °C Max -6 -6 -6 0
Cloud point °C Max -16
Calculated Cetane Index Min 45 40 40 35
Acid Number mgKOH/g Max 0.5 0.5 0.5 0.5
Oxidation stability g/m3 Max 25 25 25 25 c
Lubricity, corrected wear scar diameter (wsd 1.4 at 60°C d um Max 520 520 520 520 c
Hydrogen sulphide e mg/kg Max 2.00 2.00 2.00 2.00
Appearance Clear & Bright f b, c
a A sulphur limit of 1.00% m/m applies in the Emission Control Areas designated by the International Maritime Organization. As there may be local variations, the purchaser shall define the maximum sulphur content according to the relevant statutory requirements, notwithstanding the limits given in this table.
b If the sample is not clear and bright, total sediment by hot filtration and water test shall be required.
c Oxidation stability and lubricity tests are not applicable if the sample is not clear and bright.
d Applicable if sulphur is less than 0.050% m/m.
e Effective only from 1 July 2012.
f If the sample is dyed and not transparent, water test shall be required. The water content shall not exceed 200 mg/kg (0.02% m/m).


Parameter Unit Limit RMAa RMB RMD RME RMG RMK
10 30 80 180 180 380 500 700 380 500 700
Viscosity at 50°C mm²/s Max 10.00 30.00 80.00 180.0 180.0 380.0 500.0 700.0 380.0 500.0 700.0
Density at 15°C kg/m3 Max 920.0 960.0 975.0 991.0 991.0 1010.0
Micro Carbon Residue % m/m Max 2.50 10.00 14.00 15.00 18.00 20.00
Aluminium + Silicon mg/kg Max 25 40 50 60
Sodium mg/kg Max 50 100 50 100
Ash % m/m Max 0.040 0.070 0.100 0.150
Vanadium mg/kg Max 50 150 350 450
CCAI Max 850 860 870
Water % V/V Max 0.30 0.50
Pour point (upper) b, Summer °C Max 6 30
Pour point (upper) b, Winter °C Max 0 30
Flash point °C Min 60.0
Sulphur c % m/m Max Statutory requirements
Total Sediment, aged % m/m Max 0.10
Acid Number e mgKOH/g Max 2.5
Used lubricating oils (ULO):

Calcium and Zinc; or Calcium and Phosphorus

mg/kg The fuel shall be free from ULO, and shall be considered to contain ULO when either one of the following conditions is met:

Calcium > 30 and zinc >15; or
Calcium > 30 and phosphorus > 15.

Hydrogen sulphide d mg/kg Max 2.00
a This residual marine fuel grade is formerly DMC distillate under ISO 8217:2005.
b Purchasers shall ensure that this pour point is suitable for the equipment on board, especially in cold climates.
c The purchaser shall define the maximum sulphur content according to the relevant statutory requirements.
d Effective only from 1 July 2012.
e Strong acids are not acceptable, even at levels not detectable by the standard test methods for SAN.
As acid numbers below the values stated in the table do not guarantee that the fuels are free from problems associated with the presence of acidic compounds, it is the responsibility of the supplier and the purchaser to agree upon an acceptable acid number.

  3 comments for “Marine Fuel (ISO 8217)

  1. anirudh nansi
    5 June, 2011 at 05:43

    What is the difference between MGO and High Speed Diesel oil in terms of usage and specifications?

    • admin
      7 June, 2011 at 19:40

      I am not sure what high speed diesel as it is not any “common term” for in maritime so I guess I cannot be of any help in this case.

      Maybe there are any other reader that could give you a better reply!?

  2. 21 June, 2012 at 08:49


    Would any body highlight MGO reports with LDO?

    Can MGO be turn to LDO?

    Please advise.

    thanks & Rgds,


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