LR says December recorded the most off-spec bunker fuel cases in H2 2025, with spikes across several major ports. File Image / Pixabay

Bunker fuel quality challenges intensified in the second half of 2025, with a rise in both the frequency and severity of off-specification fuel cases across major supply hubs, according to Lloyd’s Register (LR).

About 15% of residual fuel samples tested in the second half of the year exceeded ISO 8217 limits, up around two percentage points from levels seen in the first half of 2025, LR testing service FOBAS said in its latest Fuel Quality Report released on February 4.

The period saw repeated high sulfur and catalytic-fine cases in key bunkering centres, including Singapore and Rotterdam, alongside elevated sediment and water levels in ports such as Antwerp and Hong Kong.

December recorded the highest monthly totals of off-spec incidents.

High sulfur outliers included samples testing as high as 1.85% in Rotterdam and 1.69% in Algeciras, while Singapore returned extreme cat-fine results of up to about 580 mg/kg.

Such levels can be difficult to treat onboard and may pose operational risks for engines and fuel supply systems.

The report said the main drivers of off-spec results remained broadly consistent - sulfur, stability, cat-fines and water - but several severe outliers and late-year clustering of cases underscored ongoing supply-chain variability as new blends and feedstocks enter the market.

LR advised operators to maintain strict supplier vetting, laboratory testing and onboard fuel management practices as the industry moves into a more complex fuel mix in 2026.

The full report can be downloaded here.