Renewed VLSFO Quality Concerns Threaten Ship Operations

Ship operators are facing a resurgence of fuel‐quality problems with very low sulphur fuel oil (VLSFO), the most widely used compliant bunker fuel. 

Rising levels of sediments and impurities risk accelerated wear in engine components, clogged filters, purifier failures and even complete system blackouts, leading to costly unplanned stoppages.

“Bunkering with off-spec fuel continues to be a real issue,” said Managing Director of condition-monitoring firm CM Technologies, David Fuhlbrügge. 

“The transition from traditional fuel oils to VLSFO has created ongoing problems for ship operators, with fuel quality issues becoming a persistent concern across major bunkering hubs since the introduction of the fuel more than ten years ago”.

An Integr8 Fuels report in January 2025 found that over 45% of global VLSFO deliveries failed to meet ISO 8217 specifications. CM Technologies’ own data from Q2 2025 showed more than half of tested VLSFO samples exceeded sediment limits, attributing the rise to poor blending practices and barge contamination.

Independent testing agencies Bureau Veritas, VeriFuel, VPS and FOBAS highlighted Europe as a hotspot for off-spec VLSFO. 

In Skagen, Norway, 84% of samples were off-spec, while in Piraeus, Greece, one in eight deliveries failed quality checks. Operators also report higher levels of catalytic fines and unexpected viscosity swings in the Amsterdam–Rotterdam–Antwerp corridor.

CM Technologies stressed that catalytic fines pose an immediate threat to injectors and high-pressure pumps, acting like microscopic sandpaper on critical surfaces. 

“VLSFO is a persistent problem for ship managers and charterers,” said Fuhlbrügge. “Operators must know exactly what is going into their tanks. Effective monitoring onboard and at the bunkering port is the only way to protect machinery, safeguard operations, and preserve reliability”.

Sediment, sludge and wax formation, with low-viscosity VLSFO stored above 21°C, further increase the risk of blocked filters, reduced combustion efficiency and higher fuel consumption.

To protect machinery and maintain reliability, CM Technologies recommended on-site testing both at the bunkering port and aboard vessels. 

In 2022 more than 200 ships in Singapore were halted by contaminated fuel worth over $120 million, and a 2023 Houston incident spread impurities to vessels calling in Singapore.

With emissions regulations prompting wider VLSFO use, shipowners and charterers must insist on robust fuel-quality monitoring before bunkering. Effective sampling and test-kit deployment offer the best defence against operational disruptions and safeguard both engine health and voyage schedules.
 

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If you need to resolve a dispute over fuel quality, or require support with the transportation of fuel cargoes, Brookes Bell’s team of experienced experts is here to assist.

We recognise that fuel cargo and fuel disputes can be complex and require the input and expertise of multiple experts from different disciplines. That’s why we have a multidisciplinary team of experts based at strategic maritime hubs across the world.

To learn more about our services, contact our team today.
 

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