Every ship that isn't wind- or nuclear-powered runs on some form of marine fuel, and the grade it burns is one of the most consequential — and most regulated — decisions in commercial shipping. For traders and importers looking at TOO Crude Oil's product range, "bunker fuel" often appears as a single line item next to crude oil and diesel. In practice it covers a family of products with meaningfully different specifications, regulatory status, and sourcing logistics.
What Counts as Marine Fuel
Marine fuel, or "bunker fuel," is any fuel used to power a ship's main and auxiliary engines. It splits broadly into two categories: residual fuel oils (heavy, viscous products left over from the crude refining process) and distillate fuels (lighter, cleaner-burning products like marine gasoil). Historically, large ocean-going vessels ran almost exclusively on residual fuel oil because it was the cheapest option available in bulk — a ship burning tens of tonnes of fuel a day has a strong incentive to use the lowest-cost grade its engines can tolerate.
Before 2020, the dominant grade was Intermediate Fuel Oil 380 (IFO 380), named for its viscosity of roughly 380 centistokes at 50°C. A lighter cousin, IFO 180, was also common. Both were residual fuel oils with sulphur content that could run as high as 3.5% by weight — a figure that became the centre of a major regulatory shift.
The IMO 2020 Sulphur Cap
On 1 January 2020, the International Maritime Organization's global sulphur cap took effect under MARPOL Annex VI, cutting the maximum sulphur content of marine fuel used outside designated Emission Control Areas from 3.5% to 0.50% by mass. Inside Emission Control Areas — which cover the Baltic, North Sea, and coastal waters of North America — the limit is tighter still, at 0.10%.
This single rule change reshaped the bunker fuel market almost overnight. Refiners and blenders needed to produce a new category of product — Very Low Sulphur Fuel Oil (VLSFO) — that met the 0.50% cap while still functioning as a viable heavy fuel for large marine engines. Unlike the older IFO grades, which were reasonably consistent in composition from one refinery to the next, VLSFO is typically a blend of various low-sulphur residual and distillate components. That means two VLSFO cargoes from different suppliers can behave differently even though both meet the sulphur specification, which is why compatibility testing before mixing bunker fuel from different sources is now standard advice across the industry.
Shipowners had three broad compliance paths available: switch to VLSFO, switch to marine gasoil (a fully distillate product with naturally low sulphur content but a higher price), or keep burning higher-sulphur fuel and install a scrubber — an exhaust gas cleaning system that removes sulphur oxides from the ship's emissions to an equivalent standard. Each path has different capital and operating cost implications, and the relative popularity of scrubbers versus VLSFO has shifted over time with the price spread between high- and low-sulphur fuel.
Where Ships Actually Bunker
Bunkering — the physical delivery of fuel to a vessel — concentrates heavily around a small number of global hub ports, for the same reason petroleum trading concentrates around major terminals: ships need fuel where their trade routes already take them, and suppliers need storage and berth access to serve them efficiently.
Singapore is the largest bunkering port in the world by volume, followed by ports including Fujairah in the UAE and Rotterdam in the Netherlands — the same three regions where TOO Crude Oil holds terminal positions, alongside our fourth terminal at Houston serving the US Gulf Coast bunkering market. Fujairah in particular benefits from its position just outside the Strait of Hormuz, making it a natural stopping point for vessels transiting between the Persian Gulf and the Indian Ocean without needing to detour into the Gulf itself.
Bunkering typically happens one of three ways: alongside a berth while the ship is loading or discharging cargo, at anchorage via a bunker barge that comes alongside, or ex-pipe at a dedicated bunkering terminal. Barge delivery is the most common method at high-traffic hub ports, since it lets a vessel take on fuel without occupying a cargo berth.
Quality and Documentation
Every bunkering operation is accompanied by a Bunker Delivery Note (BDN), a document mandated under MARPOL Annex VI that records the quantity, sulphur content, and other specification details of the fuel supplied. It is the document a ship presents during a Port State Control inspection to demonstrate regulatory compliance, and disputes over BDN accuracy are one of the more common sources of friction between bunker suppliers and shipowners.
Quality itself is governed by ISO 8217, the international standard covering marine fuel specifications across all common grades — density, viscosity, sulphur content, water content, and a range of contamination limits. A representative sample is drawn during delivery using a continuous drip sampler at the vessel's manifold, sealed in front of both the supplier's and the ship's representatives, and retained for independent laboratory testing if a quality dispute arises later. This mirrors the independent inspection process used for crude oil and refined product cargoes more broadly — the same inspection houses (SGS, Intertek, Bureau Veritas) that verify our crude, diesel, and jet fuel shipments also handle bunker fuel testing.
Sourcing Bunker Fuel From TOO Crude Oil
We supply IFO 180/380 and IMO 2020-compliant VLSFO from our Rotterdam, Houston, Jurong, and Fujairah terminals, on both delivery ex-pipe and vessel-to-vessel transfer, backed by the same independent quality verification standard applied to every other product line we handle. Buyers evaluating bunker fuel alongside other cargo — for example, a trading house managing both crude oil purchases and its own shipping fleet's fuel needs — can source both through the same terminal network and documentation process described on our global fuel logistics and terminal operations pages.
Frequently Asked Questions
What is the difference between IFO 380 and VLSFO?
IFO 380 is a traditional heavy fuel oil with a viscosity around 380 centistokes and sulphur content that, before IMO 2020, was commonly as high as 3.5%. VLSFO (Very Low Sulphur Fuel Oil) is formulated to meet the 0.50% global sulphur cap while targeting similar viscosity ranges, but it is a blended product rather than a single consistent specification, which is why compatibility testing matters when switching suppliers.
Can ships still use high-sulphur fuel oil (HSFO)?
Yes, but only if fitted with an exhaust gas cleaning system (a "scrubber") that reduces sulphur oxide emissions to an equivalent standard. Scrubber-fitted vessels can continue bunkering HSFO, which is typically priced below VLSFO, while non-scrubber vessels must use VLSFO, MGO, or an alternative compliant fuel.
What is a Bunker Delivery Note?
A Bunker Delivery Note (BDN) is the mandatory document issued at every bunkering operation, recording the quantity and specification of fuel delivered, in accordance with MARPOL Annex VI. It is the ship's primary evidence of fuel compliance during a Port State Control inspection.
How is bunker fuel quality tested?
A representative sample is drawn during the bunkering operation using a continuous drip sampler at the vessel's manifold, sealed in the presence of both parties, and sent to an independent laboratory (commonly the same inspection houses used for cargo — SGS, Intertek, Bureau Veritas) for analysis against the ISO 8217 marine fuel standard.
Related Reading
How we manage freight, insurance, and delivery across our terminal network.
Explore our four port terminals, including bunkering capability at Fujairah.
How vessel berthing and product transfer work at our terminals.
Discuss bunker fuel availability and specifications with our team.
