Bunker fuel testing and marine surveying business Maritec-Naias on Friday (12 June) issued an alert regarding high levels of catalytic fines and elevated acid numbers present in multiple VLSFO bunker samples from deliveries in the Singapore port: 

During the period of 20 May 2026 and 02 June 2026, Maritec Pte. Ltd. (hereafter referred to as Maritec-Naias) conducted testing on five samples representing Very Low Sulphur Fuel Oil (VLSFO) deliveries from two suppliers in the Singapore port. The analyses revealed Aluminium and Silicon (Al+Si) concentrations ranging from 61 mg/kg to 68 mg/kg.

It is important to note; these values exceed the ISO 8217:2010/2017 specification limit of 60 ppm but remain within the permissible tolerance limit of 72 ppm under ISO 4259 for a single test result. In this regard, Catalytic Fines content, (Aluminium+Silicon), above 60 ppm is regarded as high. Of the five samples, three originated from one supplier, while the remaining two were from another.

Aluminium and Silicon constitute the principal classes of abrasive solids in fuels. Elevated concentrations of such particles at the engine inlet can precipitate abnormal wear and tear of fuel system components, piston rings, and cylinder liners. To safeguard against this, many engine manufacturers stipulate a maximum threshold of 15 mg/kg Al+Si at the engine inlet.

The primary method of mitigating Catfines is through an efficiently operating fuel purification system. Monitoring Aluminium and Silicon levels both before and after centrifugation provides a reliable measure of the system’s effectiveness in removing these contaminants.

During a similar period, Maritec-Naias also tested fifteen bunker fuel samples representing VLSFO that exhibited elevated Acid Numbers, ranging from 2.0 mg KOH/g to 2.5 mg KOH/g. While these values remain within specification limits, they are nonetheless considered at higher side. Elevated Acid Numbers may stem from contamination with acidic compounds such as Phenolic compounds and Alkyl Resorcinols, often associated with Estonian Shale Oil. Such contaminants can lead to operational complications including sludge formation, fuel pump seizures, and compromised injection equipment cleanliness.

Maritec-Naias Recommendations

• High Catfines monitoring: Maritec-Naias advises collecting samples at critical points within the fuel system — including the fuel oil tank transfer pump, before and after centrifuge, service tank, and after fine-filter — to evaluate the efficiency of fuel cleaning.
• Elevated Acid Numbers: For fuels with elevated Acid Numbers, Maritec-Naias recommends conducting Gas Chromatography-Mass Spectrometry (GC-MS) using the Solid Phase Extraction (SPE) method to identify the specific acidic compounds present or upgrading your marine fuel testing package to MFTP Plus, which enables pre-emptive monitoring to detect major harmful substances prevalent in the market, such as Cashew Nut Shell Liquid (CNSL), Phenolic compounds and Alkyl Resorcinols that cause damage to equipment.

Maritec-Naias states, while all data and findings presented in this document are true, it does not reflect on the overall quality of fuel being supplied in Singapore region. If you intend to bunker at this region, please request for a Certificate of Quality (CoQ) prior to loading.

Photo credit: Hans Reniers on Unsplash
Published: 15 June, 2026

Captain Rahul Choudhuri, President of Strategic Partnerships at marine fuels testing company VPS, on Monday (8 June) offered insight and advice on how to manage fuel quality onboard idle vessels in the Gulf region: 

The Current Situation

Since the closure of the Strait of Hormuz to most commercial shipping in late February 2026, an estimated 1,550 vessels, carrying approximately 20,000 seafarers, have been unable to transit, or have chosen to remain at anchor in the Arabian Gulf, Gulf of Oman, and approaches. Traffic through the Strait, which normally averages around 138 vessels per day, has fallen to near-zero on most days. The conflict began on 28 February 2026, resulting in vessels being idle for approximately 90 days. Many are expected to remain idle until a navigable resolution to the situation emerges, which cannot be predicted at this time.

For vessel owners and operators responsible for such vessels, there is a need to focus on the technical consequences of extended idle upon fuel quality and what needs to be done in order to protect the vessel, crew and the environment.

Fuel Quality Deterioration During Extended Idle

Fuel deterioration in idle vessels is caused by a combination of time, temperature, water ingress, and inactivity. Each mechanism reinforces the others. The Arabian Gulf summer (June–September) is one of the most demanding storage environments in global shipping, with bunker tank temperatures on unshaded anchored vessels regularly reaching 50–55°C.

Biofuel Blends

The UAE, principally Fujairah and Jebel Ali, has begun supplying ISCC-certified marine biofuel blends, primarily FAME (UCOME) blended into VLSFO, at concentrations typically ranging from B10 to B30 (10–30% FAME by volume). Vessels that bunkered Biofuel blends before going idle face additional degradation risks that do not apply to conventional fuel:

FAME (UCOME) blends, may exhibit reduced storage stability. Although storage life varies, a typical shelf life is often considered to be around 3 to 4 months, after which the risk of oxidation, acid formation and microbial contamination may increase, particularly under elevated ambient temperatures.

FAME is hygroscopic and absorbs water from tank atmospheres, promoting microbial growth at rates significantly higher than conventional VLSFO. Here, the free-water monitoring frequency should be doubled for any tank containing a biofuel blend.

FAME can cause filter blockage. Depending on feedstock composition, may be susceptible to crystallisation at lower temperatures. Therefore, Wax Appearance Temperature testing should be performed before re-activation for any vessel sailing to cooler latitudes post-Gulf.

Note: The full article by VPS can be viewed here.

Photo credit: VPS
Published: 9 June, 2026

Thomas Schmidt, Customer Account Manager of marine fuels testing company VPS, on Monday (18 May) highlighted how the company’s rapid, high quality marine fuel quality testing service continue to support the global shipping fleet, through a global network of strategically positioned laboratories, on-line logistics service and over 45 years of experience:

In today’s rapidly evolving marine fuel landscape, fast turnaround times for bunker fuel analysis have never been more critical.

Stricter environmental regulations and wider use of alternative fuels has generated increasingly complex marine fuel types and chemistries. In combination with volatile global supply chains and ongoing geopolitical instability, the need for ship operators and technical managers to have rapid and reliable fuel quality intelligence is increasingly important to protect their vessels, crew, operations, and commercial interests.

Following the introduction of IMO 2020, followed by further global and regional environmental legislation geared towards IMO2030/50, there has been a continuous development of lower-sulphur and low-carbon marine fuels, resulting in fuel quality variability across the global bunker market. Different blend components, cutter stocks, additives and bio-components can result in highly variable fuel behaviour and operational compatibility challenges.

At the same time, geopolitical developments continue to reshape global energy and bunker supply chains. Traditional product flows and refinery sourcing routes are changing, creating additional uncertainty around bunker fuel composition and quality consistency. Notably in 2026, the off-specification rate of fuels to relevant ISO8217 standards increased to 8.5%, from 6.8% during 2025.

Against this backdrop, timely fuel quality testing by an accredited laboratory is essential and remains one of the most effective tools available to ship operators, as advised by all major P&I Clubs. This helps to mitigate operational and financial risk by validating against ISO8217 specifications and providing operational guidance to onboard crew for effective handing and use.

Importance of Speedy Results

Fast turnaround time is critical for several reasons:

• To assess fuel quality before the fuel is fully consumed onboard. Current fuel off-specification levels are 8.5% i.e. one in every twelve fuels has at least one off-specification parameter.
• To identify potentially problematic fuels at an early stage.
• Support fuel segregation, purification, compatibility and handling decisions.
• Preserve contractual and claim-related rights, including applicable notification and potential time-bar requirements.
• To reduce the risk of machinery damage, operational interruptions, delays, off-hire situations and costly troubleshooting cases. The Swedish P&I Club stated the average cost of a single marine fuel-related issue is >$330K.

The total turnaround time of a bunker sample is driven by a number of processes beginning with fuel delivery to the vessel and involves multiple critical stages:

1.   Ensuring the taking of a representative fuel sample, (via a VPS manual drip sampler fitted at the vessel manifold).
2.   Transfer of the sample to the local agent.
3.   Sample Transfer via Courier to the laboratory.
4.   Sample registration and laboratory analysis according to ISO8217 and additional testing requirements.
5.   Technical review, interpretation and operational advice.
6.   Report test results and advisory comments.

In many cases, the transportation phase alone may consume several days before the sample even arrives at the laboratory. 

How VPS Ensures Faster Turnaround Times

VPS has developed a fully integrated global fuel testing and advisory infrastructure, which currently boasts 93% of samples are reported within one working day from receipt in the laboratory.

SampLogic – Accelerating Sample Logistics to speed up transfer of sample to Lab

The VPS SampLogic platform is an online logistics and tracking solution designed specifically for marine fuel sample transportation, which is free for VPS customers and can save at least one full day on sample transportation. VPS Samplogic

SampLogic enables:

• Online booking of bunker sample collection.
• Automated generation of shipping documentation.
• Shipment tracking and milestone visibility.
• Faster coordination between vessel, agent, courier and laboratory.
• By reducing manual processes and improving shipment transparency, SampLogic helps minimise transportation delays and accelerates the overall testing process.

Strategic Global Laboratory Network

VPS operates a global network of wholly-owned, ISO17025 accredited, marine fuel testing laboratories strategically located across the world’s major bunkering hubs in order to support the needs of our shipping customers.

The laboratories positioning further reduces sample transfer times whilst also providing important operational resilience and redundancy. During periods of geopolitical disruption, natural disasters, strikes or unexpected regional events, samples can be redirected within the VPS laboratory network to maintain continuity and avoid delays.

Technical Advisory Support

Analytical results alone are not sufficient in terms of assessing fuel-related operational requirements, fuel management and handling, or environmental compliance. It is the expert and experienced interpretation and advisory guidance which is where the major added-value is delivered to vessels from any fuel testing service.

VPS technical advisors and marine engineers located across the global laboratory network support customers with:

• Troubleshooting.
• Fuel management recommendations.
• Risk assessments.
• Operational guidance.
• Dispute and claims support.

Where urgent fuel quality concerns are identified, VPS technical teams proactively contact customers to support immediate operational decision-making, with samples and results able to be progressed at pace, with VPS having supported numerous vessels in providing urgent results in the same working day to meet operational needs.

24/7 Digital Access Through VeriSphere

Through the VPS VeriSphere digital ecosystem, customers have continuous access to:

• Analytical reports
• Fuel quality trends
• Historical fuel data
• Market intelligence
• Digital fuel management tools
• Operational insights

This provides technical managers and vessel operators with rapid access to critical information anytime and anywhere.

In addition, the unique VPS PortStats, MyFuels and MySeparators, on-line applications within Verisphere, can provide deeper insights into global and regional fuel quality and key procurement indicators, plus operational and purifier performance improvements.

Conclusion

In the current climate, bunker fuel analysis is no longer simply a compliance exercise – it is an essential operational and procurement risk management tool.

As marine fuels continue to evolve and global supply chains become increasingly dynamic and unpredictable, rapid and reliable fuel quality intelligence is critical to protecting vessels, machinery, operations and commercial performance.

Minimising the total turnaround time from bunker sampling through to technical advisory support is therefore essential. Through its integrated logistics systems, strategic laboratory network, technical expertise and digital solutions, VPS continues to support the industry with fast, resilient and operationally focused fuel quality services.

Photo credit: VPS
Published: 19 May, 2026