Very low sulphur fuel oil (VLSFO)
VLSFO is the 0.50 percent sulphur residual blend that became the default global bunker after 1 January 2020, specified under ISO 8217 Table 2.
Very low sulphur fuel oil (VLSFO) is the residual bunker blended to meet the 0.50 percent m/m sulphur limit that MARPOL Annex VI Regulation 14 applied globally from 1 January 2020. It is not a single product: VLSFO is a family of blends built from hydrotreated residues, vacuum gas oil, cutter stocks and light cycle oil, and two stems meeting the same specification can differ in paraffin content, aromaticity and stability.
The full article will set out the ISO 8217:2024 Table 2 grades that cover fuels at or below 0.50 percent sulphur, the stability and compatibility problems that made VLSFO the dominant source of bunker quality claims after 2020, the cold-flow behaviour that follows from high paraffin content, and the commingling rules that follow from it. It will contrast VLSFO against marine gas oil on price, handling and engine-inlet viscosity, and against heavy fuel oil burned behind an exhaust gas cleaning system.
The commercial half matters as much as the chemistry. VLSFO carries its own carbon conversion factor and net calorific value in the IMO emissions guidelines, its own well-to-wake default under FuelEU Maritime, and its own quoted price at every reference port, so the choice between VLSFO and distillate is a compliance, engineering and trading decision at once.