Independently held fuel oil stocks in the Amsterdam-Rotterdam-Antwerp (ARA) hub averaged 5.47 million barrels in September, an 851,000-barrel jump that lifted inventories 18% versus August, according to Insights Global data.

The build narrowed, but did not close, the gap left by the Israel-US war with Iran. September stocks still sat 15% below February levels, even after a 51% climb from the May low — the weakest point in more than a decade.

Where did the barrels come from?

ARA fuel oil imports fell to 266,000 barrels per day in September, down from 342,000 b/d in August, Vortexa cargo flows data show. Mexico supplied 19% of inbound volumes, Colombia 13% and Benin 12%.

Exports climbed in the opposite direction. ARA shippers sent out 177,000 b/d of fuel oil last month, up from 144,000 b/d in August, with Singapore taking 21%, Spain 19% and Saudi Arabia 15%.

What about gasoil and middle distillates?

Gasoil inventories — covering diesel and heating oil — added 513,000 barrels to reach 12.59 million bbls, a 4% gain on August. Imports rose to 197,000 b/d from 155,000 b/d, led by the US (29%), the UK (20%) and Saint Lucia (12%).

Why does bunker fuel remain tight despite the build?

Physical availability at ARA bunker berths has not kept pace with the inventory rebound. A trader told Engine that prompt supply is constrained and buyers should expect lead times of five to seven days for solid coverage. The same trader flagged "some loading issues with fuel oil grades" that have slowed barge stems at terminals.

For shipowners and operators calling at Rotterdam, Antwerp or Amsterdam, the message is mixed: stocks have rebuilt meaningfully, yet short-term stems still require planning further ahead than the spot market norm.

How exposed are ARA buyers to the Middle East?

The 15% deficit versus February shows the regional system has not fully replaced barrels lost during the Iran conflict. With Saudi Arabia now among the top three destinations for ARA fuel oil exports rather than a major supplier, the cargo mix has rotated decisively toward Atlantic Basin origins — Mexico, Colombia and Benin together accounted for 44% of September imports.

That rotation keeps ARA supplied for now, but it raises the cost of any disruption to West African or Latin American loadings. A single weather event in the Gulf of Mexico or a force majeure on a Colombian pipeline would translate directly into tighter Rotterdam stems.

What should shippers watch next?

The October trading window will test whether the September build holds. Stocks typically draw down into the northern European winter as utilities and bunker buyers compete for heating and marine grades. Traders will monitor Vortexa flow data for signs that Atlantic Basin imports slow or that exports to Singapore and Saudi Arabia accelerate further.

With prompt bunker lead times already at five to seven days, any fresh pull on ARA inventories could push that window wider and force operators to divert to alternative bunkering hubs such as Algeciras or Tangier.