Bunker Fuel Quality
VPS highlights importance of regular fuel system checks in preventing vessel engine damage
Steve Bee explores how regular checks can play a vital role in protecting a vessel’s engine, stressing that even bunker fuels meeting ISO 8217 standards can lead to severe engine damage if not properly managed post-delivery.
Steve Bee, Group Marketing and Strategic Projects Director of marine fuels testing company VPS, on Monday (14 April) explored how Fuel System Check Monitoring can play a vital role in protecting a vessel’s engine as engine damage can be a very costly risk for vessel operators:
Statistically, data indicates that a vessel will suffer between one and two incidences of main engine damage over the course of its operational lifetime. The average damage costs have been estimated at around $650,000 per incident, with even more damaging incidents costing up to $1.2 million per claim. Therefore, it is important to identify the main causes of this damage and understand how it can be prevented.
Prevention of damage is, of course, preferable to cure. Fuel quality and handling issues remain a leading contributor to critical main engine failures. VPS frequently observe that such issues could have been prevented through the implementation of a robust and well-structured fuel management programme onboard vessels.
A common misconception is that a fuel meeting the international marine fuel quality standard, ISO 8217, means it is “fit for purpose”. But this is definitely not the case as even fuels that are “on specification”, at the point of delivery to the vessel, can cause major engine damage if not properly managed post-delivery. ISO 8217 specifies the requirements for petroleum fuels for use in marine diesel engines and boilers, prior to appropriate treatment before use, which means that fuels should then be treated onboard between delivery and being burnt
Catalysts used in petroleum refining are made of Aluminium Silicates, which over time breakdown. The resulting, coarse, dense fragments composing of aluminium and silicon, eventually reside in the residual portion of the refining stream. Known as “Cat-Fines”, these particles are highly abrasive and can cause severe damage to vessel engine parts.
Major marine engine manufacturers recommend a fuel should contain less than 10-15 mg/kg Aluminium plus Silicon (Al+Si) at the engine inlet. However, assuming a delivered fuel meets the stringent ISO8217:2024 limits of 40-60 mg/kg Al+Si, dependent upon the fuel grade, the fuel treatment plant would have to operate at an efficiency level capable of removing 75%-83% of these highly abrasive particles in order to meet the engine manufacturers’ requirements.
Furthermore, the International Council on Combustion Engines’ (CIMAC’s) recommendation regarding fuel quality states “Fuel analysis is the only way to monitor the quality of fuel as delivered at the time and place of custody transfer, before and after the fuel cleaning onboard and at the engine inlet. Regular monitoring of the fuel cleaning plant will provide information, which will help to make decisions about the maintenance cycles of the equipment as well as potential engine problems resulting from malfunctioning or inadequate operation.”
Yet one of the most important, but often overlooked processes, is that of regular Fuel System Checks (FSCs) in order to assess the level of aluminium and silicon catalytic fines within fuel. The presence of “cat-fines” within fuel can be extremely damaging, causing rapid engine-part wear. Monitoring cat-fine levels before they can enter vessel engines, can prevent such damage. Therefore, sending samples for analysis which are taken Before & After purification processes, on a quarterly basis is the most effective way to monitor cat-fine levels. FSCs will also help comply to the engine manufacturers general recommendation of a maximum of 10-15 mg/Kg level of cat-fines in the fuel, entering the engines and assess purifier efficiency.
There are numerous reasons why regular fuel system checks are critical:
- Help identify potential risks & operational issues before major damage occurs.
- Confirm that the system’s flow rate, temperatures, discharge cycles are properly adjusted to handle the specific fuel that is being treated
- Verify that the fuel treatment system is properly maintained
- Reduce operating cost and increase lifecycles of critical components
- Identify presence of unusual components that can enter fuel post- delivery.
Periodic sampling from the fuel treatment system will also identify problems such as water ingress from ballast systems, leaking heating coils and cargo contamination. The last thing anyone wants to see is a purifier working as a pump!
A prime example and case study is highlighted below:
An LPG Tanker bunkered HSFO in Fujairah where its fuel met ISO 8217 specifications. However, after using the bunkered fuel, the Chief Engineer reported the main engine expansion tank low level alarm, with the main engine exhaust gas temperature high on cylinder unit 2 & 4. The vessel commenced a gradual slowdown of the main engine. The Chief Engineer reported the vessel was unable to run the engine due to suspected leaks on the main engine cylinders. The vessel drifted for about 10 hours before dropping anchor off the coast of India.
Upon dismantling the engine, the following findings were made:
The VPS Technical Advisor recommended the vessel submit fuel system samples and upon checking, the results from the system, these indicated that the purifier was in fact only working like a pump.
The screening size of Al+Si on the before engine sample further confirmed why the vessel was having problems, as the physical size of Al+Si particles ranged: 5-45 µm.
The ideal particle size range of cat-fines that can be effectively removed by a marine vessel’s purifier system typically falls between 5 to 15 µm. Purifiers are designed to target these smaller particles, as they are the most common size found in heavy fuel oil and can cause significant wear and damage to engine components
If the particle size of catalytic fines is greater than 15 µm, it can pose significant risks to marine engines. Larger particles are more abrasive and can cause severe wear and damage to critical engine components such as cylinder liners, piston rings, and fuel injectors.
Note: The full article by VPS can be found here.
Photo credit: VPS
Published: 15 April, 2025
Bunker Fuel Quality
VPS: High bunker prices meet declining fuel quality
Of the current 29 Bunker Alerts issued by VPS from January to July 2026, the combination of abrasive issues due to elevated cat-fines, plus fuel stability issues, account for 72% of these alerts.
Steve Bee, Group Marketing and Strategic Projects Director of marine fuels testing company VPS, on Monday (24 August) reviewed 2026 marine fossil fuel quality to date and the high number of issues being witnessed:
Marine fuel buyers entered 2026 facing a perfect storm, suffering some of the highest bunker prices ever experienced, paired with a sharp and concerning decline in fuel quality. Across the traditional marine fossil fuel supply chain, VPS has seen a marked rise in fuel quality issues, with the Middle East conflict playing a major role in driving both price volatility and quality deterioration. For ship owners/operators, the message is clear, today’s fuel market is not only more expensive, it is also becoming more complex and unpredictable, with a higher degree of operational risk.
This deterioration is already showing itself in the test data VPS have produced. Between January and July 2026, VPS issued 29 Bunker Alerts, more than the total issued across the whole of 2024 and already closing in on the 37 alerts recorded throughout all of 2025. In just seven months of 2026, the scale and frequency of these alerts underline a clear, accelerating rise in fuel quality problems across the industry. Of the current 29 Bunker Alerts issued so far, Jan-Jul 2026, the combination of abrasive issues due to elevated cat-fines, plus fuel stability issues, account for 72% of these alerts. The ports requiring cat-fines and/or stability-related bunker alerts were, ARA, Balboa, Busan, Callao, Hamburg, Houston, Las Palmas, Philadelphia, Piraeus, Rotterdam, San Roque, Singapore and Valencia.
What is of additional interest is that marine gas oil does not account for a single Bunker Alert so far in 2026. It is HSFO and VLSFO dominating the fuels requiring such warnings.
Looking at the rate of off-specifications across each of the main marine fossil fuel types, HSFO is currently running at 8.87% of samples tested, being off-specification for at least one ISO8217 test parameter, whilst VLSFO has 9.88% off-specification level, MGO has 9.03% and ULSFOs is at 19.58%. ISO 8217 provides specification requirements for marine fuel as delivered to the ship. From a commercial perspective the fuel is only required to meet the specification at the point of custody transfer, ie at the ship’s manifold. However, compliance at this point, is not a guarantee of assurance that the fuel can be used without operational difficulties throughout its onboard lifecycle. This includes, how the fuel is stored, treat and consumed in main engines, generator engines, boilers, or other machinery. The condition of the fuel which ultimately reaches the machinery, is also strongly influenced by onboard fuel management, including storage and settling temperatures, settling time, purification temperature and throughput, purifier configuration and desludging arrangements, filtration, maintenance of the correct injection viscosity and other operational factors.
This is why knowing the characteristics of the bunkered fuel is critical to managing it correctly onboard. Appropriate testing can identify characteristics which, although not necessarily resulting in an ISO 8217 specification failure, may warrant additional operational attention. VPS therefore evaluates bunker fuels not only against the applicable specification requirements, but also provides operational advice where analytical findings indicate that additional precautions may be appropriate during storage, treatment or consumption.
VPS testing and observations, based on over 45 years of marine fuel testing experience and expertise, strongly align with a recent Linkedin post by marine and energy consultants, Brookes Bell. Their post highlighted a growing concern within the industry, stating a P&I Club had reported that bunker-related claims are up 50% this year, with many of the fuels involved having technically passed ISO8217 standard specification testing.
The same post noted that some ISO8217-compliant fuels have still caused operational damage. This has left shipowners to manage complex evidentiary disputes after problems arose. Its key warning was clear: Standard compliance testing alone isn’t catching the problem. If “passing spec” is not necessarily the same as being “safe-to-burn”, then the critical question becomes, “What additional testing is needed to identify the real operational risks?”
VPS have recognised that for some time, the ISO8217 standard is not an all-encompassing set of tests providing the highest level of asset, crew and environmental protection. For this reason, VPS offer a range of additional tests, as well as our Additional Protection Service (APS) test bundles. For example in the case of avoiding damages from cat-fines, the Fuel System Check (FSC) service, can provide valuable information in regard to monitoring purifier efficiency and the removal of cat-fines, protecting the engine to a higher degree. Whereas, Separability Number testing, is a key compliment to the hot filtration stability tests of TSP, TSA and TSE in mitigating stability risks. Should additional cold-flow information be required, the VPS proprietary Wax Appearance Temperature (WAT) testing provides key storage and fuel transfer temperature information. Whilst the VPS chemical screening services can identify potentially harmful chemicals within a fuel before the fuel is burnt. Then more detailed Gas Chromatography Mass Spectrometry (GCMS) forensic analysis provides key information to potentially support the fuel claims process.
VPS account managers and technical specialists can help shipowners and operators determine which laboratory tests are most appropriate for their fleet, based on the fuel characteristics, vessel operations and potential risk exposure. This guidance can support the mitigation of risks linked to engine damage, SOLAS compliance, legislative requirements and wider operational reliability.
The VPS Technical Advisory Team reviews bunker analysis results together with the vessel operational observations to provide practical advice on fuel storage, handling, purification and overall fuel management. Where appropriate, additional laboratory tests, or test bundles, may be recommended to further evaluate the fuel and assist in identifying the cause of an operational issue, supporting more informed decision-making.
VPS continues to monitor regional and global fuel quality trends through its laboratory network and customer feedback. Information received from vessels experiencing similar operational issues is valuable in helping VPS identify emerging trends and provide timely technical guidance to the wider shipping industry.
Photo credit: VPS
Published: 25 August, 2026
Bunker Alerts
Low flashpoint found in Indonesia bunker fuels, alerts Maritec-Naias
Firm tested eight bunker samples representing LSMDO and B40 fuel grade from vessels that took fuel oil /bunkered in Indonesia ports, which indicated flashpoints as low as 39.5°C.
Bunker Alerts
Maritec-Naias: High levels of Phenolic compounds in China bunker fuels
Firm tested multiple fuel oil bunker samples from vessels that took fuel/bunkered in China ports from 7 June to 28 July, which indicated the presence of high levels of Phenolic compounds.
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