Fuel oil's front-month contract settled at ¥4,434/t, up 0.36%, while bitumen on the same residue chain fell 3.5% to ¥5,013/t. The ¥579/t inversion signals a refiner decision on where to route residue — bunker fuel or road paving.

IMO2020 split marine fuel into two tiers: VLSFO at 0.5% sulfur and HSFO at 3.5% sulfur that can only be burned behind a scrubber. The gap between them decides whether the world's 6,000-plus scrubber-fitted vessels actually earn their keep. A wide spread lets HSFO burners cover scrubber depreciation with fuel savings to spare; a narrow spread flips the advantage back to compliant low-sulfur tonnage.

The line that matters sits near $120/t. Above it, an open-loop scrubber fleet banks tens of thousands of dollars per voyage; below it, low-sulfur tonnage wins on operating cost. With Brent above $102, the heavy end is not cheap, and refiners lean toward pulling residue into VLSFO, squeezing HSFO supply and pushing the spread back up.

For traders running bunker procurement and transit routes, this is a monthly roll: scrubber fleet charters, low-sulfur arrival windows, and the residue-yield swing during refinery turnarounds all stack into the call on which leg to lock next month.