Definition
From 1 January 2020, MARPOL Annex VI cut the global limit for sulphur in ships' fuel from 3.50% to 0.50% — "IMO 2020". Since 1 March 2020 a ship without an approved exhaust gas cleaning system (scrubber) may not even carry non-compliant fuel for her own use. VLSFO is the fuel oil refiners blended to meet the 0.50% limit.[1]
Because VLSFOs are blends, their properties vary from one supplier to the next — stability, compatibility when mixed with another stem, and cold-flow behaviour. ISO 8217:2024 adds grades written for 0.50% sulphur fuels, so an order can name a grade designed for VLSFO rather than an older RM grade with a sulphur limit added.[2]
Practical rules: avoid commingling two VLSFO stems in one tank, ask for the compatibility and stability data, and keep the MARPOL sample. Inside emission control areas VLSFO is not enough — the limit there is 0.10%.[1]
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Sources
- [1] IMO — IMO 2020: cutting sulphur oxide emissions — https://www.imo.org/en/MediaCentre/HotTopics/Pages/Sulphur-2020.aspx
- [2] IBIA — ISO 8217:2024 marine fuel specification released — https://ibia.net/iso-82172024-marine-fuel-specification-released/
A working definition for buyers, not legal advice — the contract, the convention text and your club or class have the last word.