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Infineum: Ensuring on board operability of VLSFO bunker fuels

Some conventional fuel quality tests have struggled to provide sufficient guidance to ship operators since the introduction of VLSFOs, shares Infineum experts.

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marine fuels table 2

Rob Ashton, Infineum Marine Fuel Additive Market Manager and Dr Robert Rae, Infineum Fuel Technologist, in January published an article explaining how a simple-to-use spin test, which relates more closely to the stress factors fuels may experience on board a vessel, can give a better picture of whether VLSFOs provided into the marine marketplace are suitable for use.

There are currently two tests that are frequently used in the assessment of marine fuel stability – the Total Sediments test referenced in the ISO8217 standard and the Separability Number test (ASTM D7061). However, in a previous article (click here to read), Insight highlighted the shortcomings of these tests and showed how the Alfa Laval spin test can be used as a tool to assist mariners to determine if fuels are suitable for reliable on board operations from a stability and compatibility standpoint. The test is particularly attractive as it is a simple laboratory test using the fuel in question (with no addition of extra reagents/chemicals) and subjecting it to a short centrifugation step, which can then be correlated to actual on board operation of the ships fuel purifier systems.

In our view, the Alfa Laval spin test provides valuable support to the existing Total Sediments tests.

In the same article, we also referenced the Separability Number test (ASTM D7061), which responds to a very wide range of dispersant additives at very low treat rates and questioned whether this amount of additive offered any real benefit. In recent work we have been scoping out the potential of the spin test, including a study using a new fuel purification rig (a smaller scale version of what is used on board ship). This work suggests that a low treat rate of Infineum additive technology is effective at providing both excellent reserve stability number (RSN) response and significant on board operability benefits.

In order to understand the mechanisms at work here it is important to first explore the three test methods: Total Sediments, spin and Separability Number, in more detail.

Total Sediments test (TSP/TSA)

This test features in the ISO 8217 standard. Each test is a two-stage process featuring an aging step, (TSP is thermal aging and TSA is chemical aging) followed by a hot filtration step (TSE) through a 1.6 micron filter where a result of <0.1 mass % sediment is an acceptable result.

marine fuels table 2

The TSP is believed to be a better indicator of a fuel’s relative stability under storage whereas the TSA is thought to better represent fuels’ inter-compatibility. The Total Sediments test has served the industry well for many years. However, following the introduction of low sulphur residual fuel, the test has struggled to provide adequate protection or guidance for ship operators in assessing whether a fuel is suitable for use. For example, fuels having an acceptably low TSP/TSA (<0.1 mass % sediment) can exhibit on board issues with regard to excessive sludging, and conversely fuels having a high TSP/TSA (>0.1 mass % sediment) can operate effectively without on board issues. The 1.6 micron filter used in the hot filtration step may be contributing to the discrepancy as this does not directly equate to the filter mesh that is employed on board.

Infineum asphaltene management additives are capable of reducing TSP and TSA test results. However, high treat rates of additive are required to reduce or to break/disperse the asphaltene agglomerates into a size that is small enough to pass through the total sedimentation filter (see images below).

jan 22 spin test 1 1

Infineum additive effect in the TSP test

It is increasingly apparent that a supporting or bridging test is required, one that relates more closely to the stress factors that a fuel can experience in the supply system on board the vessel. Infineum has invested in the assessment of various tests and has determined that the Alfa Laval spin test method could help to provide confidence in operability protection to ship operators.

The Alfa Laval spin test

The Alfa Laval spin test is performed by heating the fuel in question to a defined temperature. The recommended temperature to be employed in the spin-test (and for on-board separation) is dictated by the viscosity of the fuel, as recommended by Alfa Laval. However, the temperature actually used on board may vary for other reasons and so the spin-test can be conducted at any temperature, and which reflects the intended/actual operational environment. The fuel is then placed into a temperature-controlled centrifuge where it is subjected to centrifugal force via a fixed rpm for a fixed period. Once the test is complete, the centrifuge tubes are removed and inverted so that the fuel oil drains out leaving the compacted sediment in the base of the tube. The fuel oil operability is evaluated by determining the quantity of sediment that has come out of solution from the fuel sample and settled at the bottom of the centrifuge tube. The rating system is shown below:

vlfso table

During the course of our test evaluation, we discovered that significantly lower treat rates of Infineum asphaltene management additives (relative to those required for TSP/TSA test reduction) were effective. This was the case for either maintaining fuel in optimum condition for processing through a purifier, or improving a fuel which exhibits excessive sludging without additive, as can be seen in the case below. The test VLSFO represents a severe case, which experienced on board operational issues, having a base TSP of 0.28% mass sediment i.e. well above the ISO8217 specification. In addition to this, additive treatment was ineffective at significantly improving the TSP. However, in the spin test, a low treat rate of Infineum additive has recovered this apparently unusable fuel into one that would not present issues in on board operation.

jan 22 spin test 2 v2

Low volumes of Infineum additive are effective at improving fuel that exhibits excessive sludging without additive

This spin test mimics the forces the fuel experiences as it passes through the ships purifier system and these results clearly show the disparity between the Total Sedimentation test methodology versus a test designed to assess on board operability. To further our understanding of the applicability of this test, Infineum has developed a rig using a ship’s fuel purification system and the results that obtained from the rig align closely with the spin test, showing demonstrably decreased levels of sediment in the purifier bowl.

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Additive effect in Ship Purifier Rig

Separability Number test (ASTM D7061)

The Separability Number test measures the reserve stability number (RSN) by adding a fixed volume of heptane to a toluene-diluted fuel oil sample. The measurement is obtained by scanning the sample with a near infra-red source to determine the destabilisation of the solvent-diluted fuel oil sample over a 15-minute period and then the test sample is rated.

marine fuels table

Our apprehension about adopting this test methodology has previously been reported

In our view the test can give overly optimistic results with regards to a fuel’s suitability for use.

For example, a fuel which is inherently unstable and has an excessive sludging issue, where the fuel has already flocculated, can show as a stable fuel in this test or a stable fuel (such as a high sulphur fuel oil) can show as an unstable fuel.

We have also expressed our concern that this test is extremely responsive to low treat rates of additive and could give misleading information to a ship operator as to the efficacy of an additive solution. However, recent work in scoping out the potential of the spin test, suggests that low treat rates of Infineum additive technology is indeed effective at providing operability benefits.

We have further investigated the application of the Separability Number test and the additive effect in relation to spin test results. In another problematic fuel sourced from the market, where the base TSP was high at 0.27 mass % sediment, we were able to demonstrate similar spin test findings to those above. That is to say, low treat rate of Infineum additive is effective at reducing the spin test result from unfit for use to, in this case, borderline acceptable.

jan 22 spin test 4 1

However, this problematic base fuel yielded an excellent low reserve stability number of <1 thus indicating high stability reserve in both the unadditised and additised cases which is clearly not the case.

These results, along with other testing, confirm that the Separability Number test remains unsuitable as a screener test for determining the suitability of VLSFOs.

Conclusion

Infineum has investigated the mode of action of various test methods used to determine if VLSFOs are suitable for use. These studies have established that:

  • The Total Sedimentation Test requires a supporting test to give a more accurate assessment of whether a fuel is suitable for use on board. High additive treat rates of Infineum asphaltene management additives are required to influence the test due to the small filter mesh used in the test.
  • The Alfa Laval spin test correlates well with a ship’s purifier system and can be positively influenced by low treat rates of some additives to maintain or improve fuel performance in the ships fuel purification system. It is an excellent contender as a complimentary test for the sedimentation tests above.
  • The Stability Number Test remains unsuitable to reliably distinguish between useable and unusable fuels and can be misleading with regard to effectiveness of additive solutions.

Our investigations support the view that a combination of sedimentation and spin tests along with low treat rates of Infineum additives are the best option to ensure protection for ships and peace of mind for ship operators.

Related: Infineum: Proving marine additive performance
Related: Infineum additives contributing towards sustainable shipping activities
Related: Infineum: Spin test shows promise of identifying stable VLSFOs and bunker fuels
Related: Current testing methods for VLSFO stability and compatibility may require supporting tests, says Infineum
Related: Infineum clarifies indicators from certain testing protocols about VLSFO stability
Related: Infineum publishes first Sustainability Report in conjunction with Earth Day
Related: Infineum: IMO approves emissions cuts

 

Photo credit: Infineum
Published: 10 February, 2022

 

 

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Bunker Fuel Quality

FOBAS report warns of growing operational risks from ISO-compliant bunker fuels

LR’s latest FOBAS Fuel Quality Report reveals that the biggest fuel quality risks are no longer confined to off-specification fuels, with some compliant fuels creating operational challenges.

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New FOBAS report warns growing operational risks from ISO-compliant bunker fuels

Classification society Lloyd’s Register (LR) on Tuesday (14 July) warned that ship operators are facing a growing risk from fuels that appear compliant under routine ISO 8217 testing but still present operational risks once onboard.

According to LR’s latest Fuel Oil Bunker Analysis and Advisory Service (FOBAS) Fuel Quality Report, covering the first half of 2026, off-specification fuels remain a persistent challenge. 

However, some of the most disruptive cases now involve fuels that pass routine compliance testing but show poor stability or compatibility, or contain non-conventional blend components that are only identified through more detailed investigative analysis.

Several incidents investigated highlighted this trend. In March and April, a number of vessels reported operational difficulties after bunkering fuel in a major bunkering hub. Further forensic analysis found that many of the fuels contained elevated concentrations of Estonian shale oil, in some cases estimated to be around 10-15%.

While shale oil is recognised within ISO 8217 as an acceptable blend component, FOBAS investigations found that higher concentrations can be associated with fuel instability and operational issues affecting filters, separators and fuel pumps.

The report also shows that fuel quality variability remains stubbornly high. Off-specification cases remained elevated throughout the first six months of 2026, suggesting that quality issues are no longer isolated events but a more persistent feature of today’s marine fuel supply chain.

The most common recurring issues included sulphur exceedances, excessive water content, sediment and stability problems, elevated catalytic fines, sodium contamination and low flash point distillate fuels.

At the same time, biofuels (especially FAME blends) are continuing to grow without being a primary source of quality issues. Where issues occurred in blended fuels, they were generally associated with the conventional VLSFO component rather than the FAME fraction.

The report concluded that operators will need to adopt a more proactive approach to fuel management as marine fuels become more diverse and fuel quality risks become harder to identify through routine compliance testing alone.

Greater emphasis on fuel stability, compatibility and understanding fuel composition will be critical to reducing operational disruption and maintaining vessel performance.

Murray Kirkwood, Fuel Specialist Consultant, Lloyd’s Register, said: “The findings from our latest report show that fuel quality risk is evolving. The challenge is no longer simply identifying fuels that fail specification. Increasingly, operators are encountering fuels that meet the required limits but still create operational difficulties once they are stored, handled and used onboard.

“As fuel blending becomes more complex, the distinction that matters is increasingly not between on-spec and off-spec fuel, but between fuels that are operationally resilient and fuels that are operationally fragile. Understanding that difference is becoming essential for shipowners and operators.”

The latest findings reinforced FOBAS’ long-standing view that effective fuel management increasingly depends on understanding fuel behaviour rather than relying solely on pass-or-fail specification testing.

By combining routine fuel quality monitoring with forensic investigation of operational incidents, FOBAS provides shipowners with a clearer understanding of emerging fuel quality risks as the industry continues its transition to a more diverse and complex fuel landscape.

Note: The FOBAS Fuel Insight: Fuel Quality Report H1 2026 is available at FOBAS Fuel Insight: Fuel quality reports | LR

 

Photo credit: Lloyd’s Register
Published: 15 July, 2026

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Interview

Interview: Alkagesta navigates risk from bunkering ops during turbulent times

As the industry navigates this period of uncertainty, the key question is no longer ‘what will fuel cost?’ but rather ‘will fuel be available?’, highlights Mithat Çiftçioğlu.

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Mithat Çiftçioğlu, Marine Fuels Director at Alkagesta, shared his opinion on risk management for bunkering operations under current geopolitical tensions through the April edition of shipping magazine Deniz Ticaret.

The maritime publication, part of the Turkish Chamber of Shipping (İMEAK Deniz Ticaret Odası), has given Manifold Times permission to republish the article:

Fueling Ships in Turbulent Times

From Oil Shock to Fuel Access Crisis: A New Risk Map for Maritime 2026

The final weeks of the first quarter of 2026 mark one of the most complex periods in recent years for global energy and maritime markets. The sharp rise in oil and refined product prices since February 28 may look like a classic energy shock at first glance, but developments in the maritime sector point to a far deeper structural rupture.

What is being debated in the market today is no longer just oil prices. For traders and shipowners operating in the maritime sector and bunker market, the real issue is not the price of fuel — it is access to fuel. The fundamental question in the market has shifted: not what will the price of fuel be, but will fuel even be available?

In light of the Force Majeure cancellations at Asian ports over the past two weeks, another question must also be considered: Will pre-agreed bunker supply contracts actually be delivered?

From Oil Prices to Logistical Reality

Tensions in the Middle East have created a strong geopolitical risk premium in the oil market. Brent crude briefly surpassed the $100 per barrel mark, triggering a search for a new equilibrium across markets. This will inevitably bring inflation and recession back onto the global agenda in the months ahead.

But the rise in oil prices does not only reflect the risk of supply disruption — it also signals the return of one of the most fragile chokepoints in global energy trade:

The Strait of Hormuz

Approximately one-third of the world’s oil trade passes through this narrow waterway. Around 20 million barrels of oil and petroleum products transit Hormuz daily. Any disruption here would therefore affect not only oil prices, but also global refined product flows and the bunker market directly.

Why Strategic Oil Reserves Are Not the Solution

A commonly proposed solution in energy crises is the release of strategic petroleum reserves. However, releasing these reserves does not directly resolve a bunker crisis. Strategic reserves consist of crude oil. To produce bunker fuel, the following chain must be completed:

Crude oil → Refinery → Product logistics → Bunker port

This process takes time. Strategic reserves can temporarily stabilize oil prices, but they cannot solve the access problem in the bunker market in the short term.

Furthermore, the announced reserve release of 400 million barrels, to be drawn down at a rate of 2.5–3 million barrels per day, can only cover a small fraction of the estimated daily loss from the Middle East — optimistically 8–10 million barrels, pessimistically 18–20 million barrels per day.

A Historic Surge in Bunker Fuel Prices

The per-ton price of VLSFO (0.5% sulfur) bunker fuel has surpassed $1,000, reaching approximately double pre-war levels. This also represents some of the highest prices seen since July 2022.

While prices at bunker hubs such as Singapore and Fujairah are approaching $1,100 per ton, European markets have remained comparatively lower.

The Real Problem Is Not Price — It Is Fuel Access

Obtaining bunker quotes for April has become increasingly difficult, particularly at Asian ports. Even where shipowners and traders can secure quotes, the absence of supply guarantees makes pricing extremely challenging.

A senior executive at Oldendorff Carriers summarized the situation in these words:

“We cannot price cargo because we cannot calculate fuel costs; we cannot calculate fuel costs because there is no supply guarantee.”

The CEO of Maersk has compared the current situation to the pandemic era, stating that companies are attempting to source fuel through methods they have never tried before in order to keep global shipping networks supplied.

While supply is tight and prices are near their peak in Singapore and Fujairah, Rotterdam appears relatively more balanced. However, as the conflict drags on, risk perception in European markets is also rising.

The surge in bunker prices will not only increase costs — it will also affect global maritime transport capacity. Ships are expected to reduce their speeds to conserve fuel. This could lead to a reduction in effective carrying capacity, creating new logistical bottlenecks in global trade.

The importance of working with reliable, long-term partners has never been more apparent than during a crisis such as this.

The Widening Price Spread Between Fuel Types

A notable development in the bunker market in recent weeks is the rapid widening of price differentials between different fuel types. Two spreads in particular have expanded significantly:

  • Marine Gas Oil (MGO) – VLSFO
  • VLSFO – HSFO

Rising demand for distillate products, refinery production balances, and regional supply tightness are all contributing to this widening. As a result, bunker purchases have become not merely a matter of price level, but a strategic decision tied to product type and port selection.

An Unexpected Development: Biofuels Becoming Competitive

Another noteworthy development in the bunker market is that biofuels have remained at relatively competitive price levels. This creates two important opportunities for shipowners.

On one hand, biofuels remain competitively priced in certain markets. On the other, they offer a means of compliance with new regulations entering into force in Europe — particularly the FuelEU Maritime and EU ETS frameworks, which require reductions in carbon intensity. In this context, biofuels have become a strategic option for many shipowners.

Conclusion: Active Bunker Management Is The New Normal

The 2026 bunker market presents one of the most complex energy trading environments in recent years. The rise in oil prices, geopolitical risk at the Strait of Hormuz, tightness in physical fuel supply, and widening price spreads between fuel types have made bunker fuel management more critical than ever.

The prevailing view in energy markets is that as long as the risk at the Strait of Hormuz persists, turbulence in the bunker market will persist with it. As time passes, the depletion of commercial stocks may deepen the existing supply tightness further.

For this reason, the current situation is viewed not merely as an energy crisis, but as a new stress scenario testing the logistical infrastructure of global trade.

The view increasingly heard across energy markets is this:

“As long as Hormuz remains closed, it will not be oil prices but fuel access that constitutes the defining risk for global shipping.”

Finally, for shipowners and operators, bunker strategies are shifting away from a passive purchasing approach toward a model grounded in active risk management.

 

Photo and article credit: Deniz Ticaret
Published: 7 May 2026

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Analysis

T&E: Overreliance on traditional bunker fuels costs shipping USD 395 million a day due to Iran conflict

Development has made alternative fuels increasingly more competitive, states Eloi Nordé, shipping policy officer at T&E.

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The Hormuz crisis adds over 300 million a day to shippings fossil fuels bills

The European Federation for Transport and Environment (T&E) on 27 March highlighted the adoption of green marine fuels would reduce the shipping industry’s exposure to fuel price shocks in future.

It noted shipping companies are spending an extra €340 million (USD 394.74 million) a day in additional fuel costs as a result of the latest conflict in the Gulf.

As 99% of the global fleet runs on fossil fuels, the industry is directly exposed to fuel price volatility and supply disruptions. Efficiency measures, electrification and e-fuels would reduce the industry’s exposure to price fluctuations.

According to T&E, marine fuel prices have escalated rapidly, with VLSFO reaching €941 per tonne in Singapore, up 223% since the start of 2026. At the same time, LNG prices have risen by 72% since early March. Since February 28, shipping companies have incurred more than €4.6 billion in additional fuel costs.

The development has made alternative fuels increasingly more competitive. As fossil fuel prices reach record highs again, the cost gap with e-fuels is narrowing.

T&E’s research shows that the cost gap between marine gas oil – one of the more expensive fossil fuels – and e-fuels has shrunk to near parity (+5%) in some ports.

Hormuz oil crisis boosts potential e fuel competitiveness

While the trend may be temporary, it shows that the volatility of fossil fuel markets offsets much of the structural cost disadvantage of clean fuels.

“Chaos in the Strait of Hormuz is putting global maritime trade under the spotlight. But it’s on the oil markets where its impact will be felt the most. The war is costing the industry millions every day,” said Eloi Nordé, shipping policy officer at T&E.

“Some governments and parts of the industry have spent the last year bashing green maritime measures as being too expensive, yet those costs pale in comparison to this super-disruption.

“If anything, this crisis should be the catalyst for more investment in European e-fuels and greater uptake of energy efficiency measures to avoid fossil fuel shocks in the future.”

 

Photo credit: European Federation for Transport and Environment
Published: 2 April 2026

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