Making sense of low sulphur fuel terminology: ULSFO RM/DM and VLSFO RM/DM

The arrival in the market of marine fuels meeting a 0.10% sulphur limit that were not marine gas oils (MGO) has led to a raft of names, some of which have proven to be misleading. Supply of fuels that don’t fit neatly into the traditional distillate/residual tables in the ISO 8217 marine fuel quality standard is set to increase when the market ramps up production of products meeting the 0.50% sulphur limit in 2020.

How can we make sense of this often confused terminology?

As the sulphur limit in emission control areas dropped to 0.10% in 2015, a number of alternatives to MGO – which up until then had been seen as pretty much the only compliant fuel option – appeared in the market. Some of these fuels would have fitted into the distillate table of the ISO 8217 marine fuel standard with the exception of just one or two parameters; mostly because they exceeded the maximum 11 cSt viscosity limit to meet a distillate specification. As a result such fuels have typically been sold as a residual grade such as RMD 80. Other ECA-compliant fuels are closer to residual marine specifications and some of these have been sold as RME 180 under ISO 8217.

The names given to these products have varied. Some called them all  ultra-low sulphur fuel oil (ULSFO), but some objected to this description if the product was in fact a distillate. Calling these products ‘novel’ and ‘hybrid’ fuels has also been also common, but only a few products were in fact ‘novel’ or ‘hybrid’  as they were mainly existing refinery products, products making a comeback, or blends of existing product streams. Hybrid may be a reference to how these products seem to straddle the distillate and residual tables in ISO 8217.

John Stirling, Quality Manager, World Fuel Services, told a joint forum organised by IBIA and the UK Chamber of Shipping in London last month how the fuels working group at CIMAC has come up with a few simple ground rules to make sense of fuel classification.

First of all, a key operational differentiator is whether or not the fuel needs to be kept heated to stay liquid in ships’ fuel tanks and during transfer onboard. This simple criterion could be used to determine whether a fuel should be classified as a residual marine (RM) or a distillate marine (DM) fuel. If it needs heating, it should be seen as RM. If it doesn’t, it should be seen as a distillate marine fuel oil, or DM for short.

Secondly, to separate between fuels meeting a 0.10% sulphur limit and a 0.50% sulphur limit, the terminology should be different. A solution to this would be to call fuels up to 0.10% ultra-low sulphur or ULS for short, and to call fuels that are above 0.10% but meeting a 0.50% limit very low sulphur, or VLS for short.

To keep it simple, all the products could be called fuel oil, in line with the terminology in MARPOL Annex VI which calls all fuels for marine consumption ‘fuel oils’.

This way we are left with the following terminology:

  • RM: residual marine (fuel that needs heating)
  • DM: distillate marine (does not need heating)
  • FO: fuel oil
  • ULSFO RM: maximum 0.10% sulphur RM product
  • ULSFO DM: maximum 0.10% sulphur DM product
  • VLSFO RM:  RM products that are above 0.10% but meeting a 0.50% sulphur limit
  • VLSFO DM:  DM products that are above 0.10% but meeting a 0.50% sulphur limit

Of course, the grade names in the ISO 8217 table will still be used, such as the distillate grade names DMA (clear and bright MGO), DMB and DMC (marine diesel oil grades, not required to be clear and bright) and the usual heavy fuel oil grades, e.g. RMG 380.

For gas oil, Stirling used ULSGO/LSGO to designate between products sold in the marine sector that are ultra- low sulphur and usually come from the same supply pool as automotive diesel (ULSGO), and “regular” MGOs with no more than 0.10% sulphur (LSGO). The ULSGOs coming into the market from the automotive market typically have only 10 to 15 parts per million (ppm) sulphur, or 0.001% to 0.0015%.

John Stirling presenting at the IBIA & UK Chamber of Shipping forum

We now also have the addition of a new distillate table, DF (Distillate FAME) which allows for up to 7% fatty acid methyl ester(s) (FAME) content by volume. (Read more about that here:

Report by Unni Einemo:

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