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Fuel Regulations

ISO Petroleum Marine Fuels

ISO 8216 and ISO 8217 standards describe the categories of marine fuels and provide detailed specifications, respectively. These specifications were developed to meet the requirements for marine fuels supplied on a world-wide basis for consumption on board ships. Internationally, a wide variety of residual fuel categories are available due to variations in crude oil supplies, refining methods, ship machinery characteristics and other local conditions. However, at a local or national level, the number of available categories can be limited.

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While ISO 8217 takes into account various international requirements for such properties as flash point and sulfur, it is up to the user to identify and ensure compliance with all local, national and regional requirements.

ASTM D2069, adopted in 1991, was intended to be technically equivalent to ISO 8217. It was withdrawn in 2003.

An update of ISO 8217 published in 2010 added requirements for hydrogen sulfide, acid number, oxidation stability and lubricity to distillate grades and requirements for CCAI, hydrogen sulfide, acid number and sodium content to residual grades. For residual grades, the ash, vanadium and aluminum-plus-silicon limits were reduced. Another update in 2012 added a test method for hydrogen sulfide.

The 2017 update changed the scope to allow hydrocarbons from synthetic or renewable sources to be used as well as permitting blends with biodiesel (FAME) up to 7%. For distillate fuels, new grades containing biodiesel were added, the sulfur content of some grades was reduced and cloud point and cold filter plugging point (CFPP) requirements were added. The requirements for residual grades were unchanged.

To accommodate the introduction the 0.50% global sulfur limit by the IMO in 2020, a Publicly Available Specification PAS 23263: “Guidelines for fuel suppliers and users regarding marine fuel quality considering the implementation of maximum 0.50%S in 2020,” was published in 2019 [6275]. It provided detailed guidance to fuel suppliers and users on managing the types of fuel blends that were expected to dominate the global bunker market starting in 2020 with a focus on stability, compatibility with other fuels and cold flow properties. Developing a PAS was considered the best option by ISO as there was insufficient time to revise ISO 8217:2017.

The 2024 update included the introduction of numerous new residual fuel grades [6274]. These new grades cover residual fuels with a maximum sulfur content of 0.50%, residual fuels containing biodiesel, and residual fuels with a sulfur content above 0.50%. For distillate grades, blends containing biodiesel now have no upper limit on the FAME content but have additional requirements for oxidation stability, reporting the net heat of combustion, and a minimum cetane number for FAME containing blends.

It should be noted that the bunker fuel market can be very slow to adopt updates to ISO 8217. For example, according to bunker trading company Integr8, in the six months prior to November 2023, 72.8% of its residual fuel trades and 72.4% of its distillate fuel trades were guaranteed to meet ISO 8217:2010. Only 25.8% of its residual fuel trades and 18.1% of its distillate fuel trades were guaranteed to meet the latest specification available, ISO 8217:2017. A small portion of its residual fuel trades, 1.8%, but a significant portion of its distillate fuel trades, 9.3%, were still only guaranteed to meet ISO 8217:2005 [5981].

Classification. The detailed classification of marine fuels into categories of products is based on the main applications and characteristics of the products. The classification is broadly broken down into distillate fuels and residual fuels.

The products are designated by a code that consists of:

  • the initials ISO,
  • the letter F (for petroleum fuels),
  • the category of fuel, consisting of three letters:
    • the first letter of this category is always the family letter (D for distillate or R for residual);
    • the second letter, M, designates the application “Marine” or F designates a blend containing FAME,
    • the third letter, X, A, B, C, …, Z, which indicates the particular properties in the product specification (ISO 8217),
  • for residual fuels, a number which corresponds to the maximum kinematic viscosity, in mm2/s, at 50°C.

For example, a product may be designated in the complete form, e.g., ISO-F-RMA 10, or in abbreviated form, e.g., F-RMA 10.

While not specifically covered in either of the above ISO standards, Intermediate Fuel Oil (IFO) is a blend of distillate and residual fuel. These blends are referred to with the letters “IFO” followed by the product’s viscosity (e.g., IFO 180). Some products covered in ISO 8217 are occasionally referred to as IFO. For example, ISO-F-RME 180 could be referred to as IFO 180.