VLSFO is the dominant marine fuel grade globally since the IMO 2020 sulphur cap took effect on 1 January 2020. It refers to any residual marine fuel with sulphur content at or below 0.50% by mass, covering the range of products previously designated as 380 CST, 180 CST, and their variants, now reformulated to meet the sulphur limit.
Main engine fuel for the vast majority of deep-sea commercial vessels without exhaust gas cleaning systems
Prior to IMO 2020, most deep-sea vessels burned HFO/IFO 380 with sulphur content up to 3.50%. The IMO cap cut this to 0.50% globally, forcing either a fuel switch (to VLSFO or MGO), installation of scrubbers to remove sulphur from exhaust, or a move to alternative fuels. VLSFO emerged as the commercial solution for most vessels.
VLSFO is not a single product but a family of blends. Refiners and blenders combine residual streams with lighter cutter stocks to hit the 0.50% sulphur target. This means VLSFO supplied at different ports can have materially different viscosity, density, compatibility, and stability characteristics. Careful pre-bunker testing and compatibility checks with existing onboard stocks are important.
Because VLSFO blends can contain asphaltenes in variable proportions, co-mingling fuels from different sources can cause asphaltene precipitation — sludge formation in tanks, filters, and separators. Best practice is to segregate stems from different sources or run compatibility tests before mixing.
Some VLSFO blends have elevated pour points that can cause handling issues in cold climates without adequate heating. Cat fines (aluminium and silicon residues from refinery catalytic cracking) can be elevated in some blends and require careful separator management to avoid engine wear.
Ports in our directory where VLSFO is available as a standard commercial grade:
Seven Ocean procures marine fuel at every major global hub. Tell us the vessel, the port, the grade, and we'll come back with a stem.
Request a quote →