Two ways to comply
Since the IMO 2020 sulphur cap, a vessel has two broad ways to meet the 0.50% limit: burn a compliant fuel such as VLSFO or LSMGO, or keep burning cheaper HSFO and clean the exhaust with a scrubber (exhaust gas cleaning system). The whole economic case for the second path rests on one variable.
The Hi-5 spread
The HSFO–VLSFO spread — often called the Hi-5 — is simply the price difference between the two fuels. It is the per-tonne saving a scrubber-fitted vessel captures by continuing to burn HSFO while compliant vessels pay up for VLSFO. The wider the spread, the faster a scrubber pays back.
The payback math
A scrubber for a large vessel typically costs in the region of two to four million dollars installed. Set that against the daily saving: a large tanker consuming roughly 100 tonnes a day saves the spread on every tonne. At a spread of around 300 dollars per tonne, that is roughly 30,000 dollars a day, and the capital can be recovered in a matter of months. At 150 dollars per tonne the payback roughly doubles; below 100 dollars it stretches out considerably and the case weakens.
Why the spread refuses to sit still
The spread is genuinely volatile. It has touched record lows around 60–130 dollars per tonne in quieter periods and pushed well beyond 300 dollars per tonne when conditions tighten — as it did in early 2026 amid higher crude prices and supply disruption. The drivers are the absolute level of crude, refinery output, the relatively small pool of HSFO buyers, and geopolitics affecting heavy, high-sulphur barrels. Port matters too: the spread in the Middle East is typically wider than in Northwest Europe.
The point most people miss: carbon
A scrubber removes sulphur oxides — it does nothing for carbon dioxide. So a scrubber vessel burning HSFO is still fully exposed to carbon-pricing regimes. Under EU ETS and FuelEU Maritime, and any future IMO carbon levy, HSFO carries the same (or higher) carbon cost as compliant fuels. The fuel-price saving and the carbon cost have to be weighed together, not separately.
The strategic takeaway
The owners who get the most from scrubbers plan ahead and lock in wider spreads through contracts rather than relying on spot HSFO at unfamiliar ports, where discounts are often thin. Consumption profile and trade pattern matter: a high-burn vessel on a route with reliably wide spreads is a very different proposition from a low-burn vessel calling ports where HSFO is scarce. And the carbon trajectory should sit in every calculation made today.
Frequently Asked Questions
What spread makes a scrubber worth it?
There is no single threshold, but historically a sustained spread comfortably above 100 dollars per tonne has been needed to justify new installations, with wider spreads shortening payback to months. The right number depends on capex, consumption and how long the vessel will trade.
Are scrubbers banned anywhere?
Some ports and coastal zones restrict open-loop scrubber discharge, requiring closed-loop operation or compliant fuel while in those waters. Operators need to check local rules port by port.
Does a scrubber reduce my EU ETS or carbon cost?
No. Scrubbers cut sulphur oxides, not carbon dioxide. HSFO burned behind a scrubber is still subject to EU ETS, FuelEU Maritime and any future carbon levy.
Is HSFO going away?
Not soon. HSFO is expected to retain a steady share of the marine fuel pool for scrubber-fitted tonnage, though smaller than VLSFO. Availability can be patchy at smaller ports.