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Infineum: Spin test shows promise of identifying stable VLSFOs and bunker fuels

Infineum has been evaluating various test methods to support the industry with a view to finding a new test method to better indicate the suitability of VLSFOs.

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The stability issues being reported regarding the use of very low sulphur marine fuels are often related to the fuels’ shelf life, which makes it increasingly important to assess fuel quality over extended periods. Rob Ashton, Infineum Marine Fuel Additive Business Development Manager, explains how selecting the most appropriate combination of tests to evaluate stability and compatibility over time is increasingly important in order to offer the most complete protection for ship operators:

Since the introduction of the IMO 2020 sulphur cuts, the stability of very low sulphur fuel oils (VLSFO) at point of sale has largely been on specification. However, uncertainty around the shelf life of these fuels, which can be less than three months, means this remains one of the key areas of concern for VLSFO use. This has led Infineum to invest in the assessment of the various tests that are available to help operators to ensure the fuel they have on board is suitable for use.

In a previous Insight article Sediment concerns in marine fuels, we evaluated the Separability Number test (ASTM D7061), which measures the Reserve Stability Number and is being widely used to assess fuel oil stability and compatibility. Following a thorough study of this test we concluded that it is unsuitable for determining stability and compatibility of VLSFO over the fuels’ shelf life. While we understand the rationale for employing this test, in our view, the Separability Number test methodology eliminates the natural solvency of the fuel from the equation by saturating the fuel medium with polar aromatic solvent (toluene) at between 1:3 and 1:20 ratio. This means that the test analyses some characteristics of the asphaltene species contained within the fuel, but does not assess the stability of the fuel itself, which is the most critical factor for the new VLSFOs.

This is owing to the fact that most additives targeting asphaltene management show benefits in the Separability Number test at very low treat rates. There are some commercial additives that can trigger large improvement responses in this test but are unable to demonstrate any robust level of performance in other key test methodologies (e.g. Potential Total Sediment (TSP) and S ASTM D7157 value), even at elevated treat rates. It is questionable whether the low treat rates offered for the Separability Number test are giving any tangible benefit in ensuring VLSFOs are suitable for use on board ship.

Spin test evaluation

Infineum has been evaluating various test methods to support the industry with a view to finding a new test method, which would better indicate the suitability of VLSFOs. Among the tests that have been evaluated is the Spin Test, which has been developed by Alfa Laval, a leading provider of fuel oil purifier equipment for the marine industry.

Other Spin Test methods, used for determining sediments and water and fuel oils are also available (e.g. ASTM D1796). However, these test methods generally require fuel dilution, which, once again, can impact the effect of the fuel’s natural solvency on results. One of the key attractions of the Alfa Laval test methodology is that fuel is unadulterated and is only subject to the forces likely to be experienced in ships’ purifier systems. Stokes law* is the underlying principle here.

The Alfa Laval test is carried out by heating the fuel to a defined temperature, dictated by the required viscosity of the fuel, spinning in a heated centrifuge at a fixed rpm for a fixed time period (read more). Once the test is complete, the centrifuge tubes are removed from the centrifuge 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 within the centrifuge tube. The rating system is shown below:

vlfso table

Using the Spin Test to assess operability

A severe VLSFO was selected for testing, which was off-specification for Total Sediments Potential at 0.14 mass %, versus the maximum specifications in ISO 8217 of 0.1 mass %. The Spin Test yielded a value of 1.5% sludge volume. For this particular case, the result aligns with TSP, meaning that this fuel could cause onboard issues in the purifier system and its use should be avoided.

To assess the ability of the test to discriminate the effects of additive use, a sample of the fuel was treated with Infineum asphaltene management technology. A second sample was treated with another commercially available additive at the same treat rate, which was significantly above the supplier’s recommended treat rate.

On visual inspection, the Infineum technology delivered a clear benefit, demonstrating how effective the additive is at dispersing the asphaltenes. The Spin Test result of 0.1% sludge volume confirmed these initial observations. TSP was also carried out and a reduction from 0.14 mass % to 0.01 mass % was recorded, confirming that the fuel additised with Infineum technology would be suitable for use on board.

The competitor additive offered no TSP improvement and was unable to move the fuel into a safe operating window according to the Spin Test. This result reinforces the importance of verifying additive performance in a suitable test to ensure that an actual real-world operability benefit is bestowed by the additive in the fuel oil.

vlsfo spin results 1 1

Linking performance to ship trial

A study was also undertaken to relate Spin Test performance back to a ship trial that had been carried out on a Suez Max tanker with a two-stroke engine – see case study. To recap, the fuel supplier had produced on-spec VLSFO (<0.1 mass % total sediment), which deteriorated rapidly on board ship to the point where the fuel was unusable (>0.23 mass % TSP) and had to be de-bunkered. An identical VLSFO blend was made with Infineum additive technology to give a TSP <0.04 mass %.

Samples of the components used to make the ship trial fuel had been retained and although they were 18 months older (and hence more severe in nature), it was decided to evaluate this test case in an extended Spin Test programme. Initially, TSP and Separability Number (RSN) testing were carried out over an eight-week period to assess the fuel’s performance.

At the start of the test, the VLSFO without additive was borderline off spec at 0.11 mass %, vs. <0.10 mass % in the original ship trial, but it rapidly deteriorated to 0.19 mass % after the four-week period. This level was maintained over the eight-week test period, compared with the deterioration in TSP to 0.23 mass % during use in the original ship trial blend. By comparison, the Separability Number test yielded a high stability reserve (RSN <<1) indicating that it would remain suitable for use over the whole test period, which it clearly did not.

may 21 vlsfo 1

When the VLSFO was treated with Infineum technology, it greatly improved the TSP at the start of the test down to a level of 0.04 mass % which mirrored the original ship trial result.

may 21 vlsfo 2

After four weeks, the treated VLSFO drifted off spec for TSP (0.13 mass %) albeit to a lower level than observed in the unadditised samples. It then maintained that slightly off-spec level over the eight-week period, whereas in the original field trial TSP was maintained at 0.04 mass % throughout the 15-week ship trial. Again, Separability Number returned a high stability reserve (RSN <<1) despite the fuel being off spec for TSP.  

The TSP/RSN protocol above was repeated with the Spin Test, this time over a 10-week period.

vlsfo spin shelf life 1

According to Spin Test data, the base fuel was deemed unfit for use at the start of the test (0.8% sediment) with further deterioration over the 10-week time period to 1.4% sediment. This is aligned with the TSP results.

Infineum additive technology maintained the fuel below the unfit for purpose level according to the sludge level in the Spin Test (0.3%) over the whole time period despite being borderline off spec for TSP (0.12 mass %) after the 10-week period.

This test programme builds on Infineum’s previous field experience, demonstrating that the Spin Test gives further supporting information, in addition to the Total Sediments test, that enables ship operators to assess the suitability for use of VLSFOs over an extended timeframe. It could be said that the TSP test is a low shear test environment for the fuel, similar to that experienced in storage conditions on board. However, the Spin Test is a higher shear environment (centrifugal force) mimicking purifier operation, which assesses whether sediment will precipitate from a residual fuel while passing through the fuel purifier. Both tests measure different, but relevant, stress factors that fuels experience in storage and purification and consequently offer a more comprehensive picture of how a fuel will perform on board.

Conclusion

There are differences between high sulphur fuel oil and very low sulphur fuel oil from a sediments perspective and, in our view, there is a need for additional tests to ensure the very low sulphur fuels provided into the marine marketplace are suitable for use. The Separability Number test, although historically useful for high sulphur fuel oils, is not able to predict if the new VLSFOs now in the market are suitable for use.

The TSP test, which is the existing reference test in ISO 8217 for assessing sediment, does have issues with repeatability, especially in fuels that have high results or where the performance changes over time. Regardless of this fact, it is crucial that any tests used should provide confidence in operability protection to ship operators. In this regard, the Alfa Laval Spin Test performance translates directly into improved purifier operation for ship operators. Consequently, Infineum believes that a combination of TSP and the Spin Test, coupled with effective asphaltene management additives offer the most complete protection for ship operators.

 

Photo credit and source: Infineum
Published: 7 June, 2021

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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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