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VPS publishes 2023 annual review of its findings on bunker fuels

Findings in VPS’ review include 58% of its 2023 Bunker Alerts were for VLSFO fuels, followed by 24% for MGO fuels and 14% for HSFO; most common problematic parameter was Flash Point.

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Marine fuels testing company VPS on Tuesday (16 January) published an article titled ‘2023 Marine Bunker Fuels Review’ by Steve Bee, VPS Group Commercial Director, giving insightful annual review of VPS findings on both global and regional maritime fuel matters, focusing on marine fuels. 

Introduction

2023 saw the continuing evolution and the widening of available maritime fuel types and grades, as the global shipping industry gathered decarbonisation momentum to reduce its emissions and achieve current and future legislation targets. Existing CII and EEXI requirements, the incoming EU ETS legislation, plus the slightly longer-term IMO legislation, saw increasing demand for additional testing, lower-carbon fuels, data and digitalisation solutions across the shipping sectors.

As the leading maritime decarbonisation testing and advisory services provider, VPS continued to be at the forefront of marine fuels and lubricants analysis, utilising our experience, expertise and innovative approach, to support this drive for a more sustainable shipping fleet.  

Throughout the year, VPS witnessed further fuel quality issues with VLSFOs in terms of cold-flow property issues, sulphur compliance and cat-fines. HSFO and VLSFO suffered numerous degrees of chemical contamination, whilst MGO suffered from cold-flow, flash point and FAME off-specifications.

Biofuels usage certainly gathered momentum and the increased demand from the market led to increasing queries regarding their fuel management and their “fit-for-purpose” as a drop-in marine fuel, which in turn called upon VPS to provide answers and solutions to customers, utilising our extensive knowledge and understanding of biofuels and their associated test parameters. 

The Marine Fuel Mix

Across 2023, the fuel mix with respect to samples received for testing in VPS laboratories, equated to 62.7 million MT, which is over 5 million MT of marine fuels per month. VLSFO was the most popular marine fuel with 54.3% of the fuels used, followed by 29.5% HSFO (a growth of 15.4% over 2022), 14.2% MGO, 1.2% ULSFO and 0.8% Biofuels. Regarding biofuels usage, the samples tested by VPS equated to an increase from 231,000 MT in 2022 to 558,000 MT in 2023.

VPS 2023 MARINE BUNKER FUELS REVIEW

VPS Bunker Alerts

Bunker Alerts highlight short term fuel quality issues identified by VPS, for a specific test parameter of a specific fuel grade/type in a specific port. The service provides valuable information to customers, to assist in avoiding potentially problematic fuel types in a highlighted port or region, to further protect the customer’s asset and crew.

In 2023 VPS issued 28 Bunker Alerts, eight fewer than in 2022. The 2023 Bunker Alerts included all major fuel grades, i.e. VLSFO, HSFO, MGO and ULSFO, ten different test parameters, 12 ports and 9 countries.

58% of the 2023 Bunker Alerts were for VLSFO fuels, followed by 24% for MGO fuels and 14% for HSFO. The most common problematic parameter was Flash Point, accounting for 28% of the Bunker Alerts, followed by Sodium at 24%, with Sulphur and TSP at 10% each.

Singapore (32%) and ARA (21%) were the regions/ports most frequently requiring a Bunker Alert to be issued. But as these are the two busiest bunkering regions, it is not too surprising.

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VLSFO Fuel Quality

As the most used marine fuel type, VLSFO accounts for more than half of the fuels tested by VPS. In terms of quality, Europe provided the highest level of off-specification VLSFOs in both 2023 (7.8%) and 2022 (7.9%). Africa provided the next highest level of off-specification fuels with 6.7% in 2023 and 7.0% in 2022, with North America third with 4.4% of fuels tested exhibiting at least one off-specification parameter in 2023 and 4.3% in 2022.

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Sulphur is the most common off-specification parameter of VLSFOs, accounting for 26.6% of VLSFO off-specs in 2023 and 31.5% in 2022. 0.7% of VLSFOs tested in 2023 had a sulphur level of 0.50%-0.53%, with 0.5% of samples tested having a sulphur level greater than 0.53%.

Pour Point was also a common off-specification parameter for VLSFOs with 13.6% of VLSFOs off-specs relating to this parameter in 2023 an increase over the 11.4% level witnessed in 2022. 

The importance of the additional cold-flow test of Wax Appearance Temperature (WAT) and Wax Disappearance Temperature (WDT), was highlighted in 2023 with 63% of VLSFOs exhibiting WAT of 31-40ºC and 14% having WAT between 41-50ºC. 55.7% of VLSFO samples had a WDT of 41-50ºC, with 28.1% having a WDT of >50ºC. VLSFOs cold-flow properties are a definite concern with wax precipitating from the fuel at temperatures way in excess of 10ºC above the pour point, potentially causing numerous operational problems such as filter and pipework blockages.

Sulphur is the most common off-specification parameter of VLSFOs, accounting for 26.6% of VLSFO off-specs in 2023 and 31.5% in 2022. 0.7% of VLSFOs tested in 2023 had a sulphur level of 0.50%-0.53%, with 0.5% of samples tested having a sulphur level greater than 0.53%.

Pour Point was also a common off-specification parameter for VLSFOs with 13.6% of VLSFOs off-specs relating to this parameter in 2023 an increase over the 11.4% level witnessed in 2022. 

The importance of the additional cold-flow test of Wax Appearance Temperature (WAT) and Wax Disappearance Temperature (WDT), was highlighted in 2023 with 63% of VLSFOs exhibiting WAT of 31-40ºC and 14% having WAT between 41-50ºC. 55.7% of VLSFO samples had a WDT of 41-50ºC, with 28.1% having a WDT of >50ºC. VLSFOs cold-flow properties are a definite concern with wax precipitating from the fuel at temperatures way in excess of 10ºC above the pour point, potentially causing numerous operational problems such as filter and pipework blockages.

2023 also saw a significant increase in cat-fine levels in VLSFOs, with 12.7% of all off-specifications relating to this parameter, compared to 8.5% in 2022. 16.2% of all VLSFOs showed a cat-fine level greater than 40ppm. Frequent checking of purifier efficiency via VPS’ Fuel System Checks (FSC) service is a highly recommended proactive safeguard in respect to increased cat-fines within VLSFOs.

VLSFO viscosities vary enormously depending upon to blend components used. In 2023 VLSFO viscosities ranged from <20Cst to >380Cst. 16% of all VLSFO off-specifications were due to viscosity. Only 0.5% of VLSFOs had a viscosity of >380Cst. 68% of all VLSFO viscosities were less than 180Cst. Viscosity is such a key operational parameter, determining the transfer and injection temperatures of fuel onboard ships and therefore determining the exact viscosity of VLSFOs is crucial to ensure optimal efficiency.

Biofuels

As global shipping looks towards low-to-zero carbon fuels to answer many emissions reduction challenges, biofuels offer an immediate “drop-in” solution. As such VPS tested the equivalent of over 500,000 MT of biofuels in 2023 compared to ca. 230,000 MT in 2022.

Europe, (mainly ARA-region) provided the highest volume of biofuels at almost 400K MT (ca. 74%) and Singapore second (ca. 21%), providing just over 100K MT.

The most common biofuel blend was B30 (10-30% bio), which accounted for 34.3% of biofuel samples tested by VPS. Yet, B100 (>90% bio) was not far behind with 30.1%.

The majority of biofuels contained Fatty Acid Methyl Esters (FAME) as the bio-component, although VPS did test others containing HVO, HEFA, Cashew Nut Shell Liquid (CNSL) and Tyre Pyrolysis Oil (TPO).

Where FAME is the bio-component within marine biofuels, the key considerations are:

  • Energy Content, Renewable Content
  • Fuel Stability, Cold-Flow Properties
  • Corrosivity, Microbial Growth

Of the biofuels tested by VPS in 2023, 9% of those tested for oxidation stability gave the concerning result of <5 hours, highlighting a high degree of instability, whilst 6.7% gave a result of 5-8 hours which is still a cause for concern.

In terms of corrosivity, 11.9% of those biofuels tested provided an amber/caution result, whilst 8.5% of those tested provide a red warning, indicating potential high levels of corrosivity.

It is fully expected that the growth in biofuels usage for marine applications will continue to increase across 2024 and the VPS Additional Protection Service (APS) when using biofuels, will only increase in importance as the industry looks for more information regarding the fuel management of biofuels.

Summary

2023 once again highlighted the importance of bunker fuel quality testing, as a proactive means to protect vessels, their crew and the environment. With additional tests, currently not included within ISO8217, providing further  vital information in achieving heightened levels of protection.

Whilst we can expect a new revision of ISO8217 in early 2024, additional tests will still hold an important role in fuel management.

Biofuels usage will continue to increase in demand and importance, as ship owners and operators look to achieve improvements through CII and EEXI, as well as looking to counter the financial impact of the EU ETS scheme.

Methanol demand and usage will also grow, following the recent success of Maersk’s Laura Maersk and the rapidly growing order book for methanol-powered vessels.

So 2024, suggests another year of widening marine fuel types and grades coming to market, coupled with their growing fuel management considerations.

Note: The full article titled ‘2023 Marine Bunker Fuels Review’ with related graphs and charts can be found here

Related: World’s first methanol-fuelled boxship christened and named “Laura Maersk”

 

Photo credit: VPS
Published: 30 January, 2024

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Bunker Fuel Quality

VPS on lifeboat fuel quality: A safety of life at sea critical risk

Neil Chapman and Steve Bee said regular fuel testing, correct fuel selection, and proactive fuel management are essential to ensure lifeboats are ready when they’re needed most.

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Neil Chapman, Managing Director of Americas, and Steve Bee, Group Marketing and Strategic Projects Director of marine fuels testing company VPS, on Monday (13 July) said regular fuel testing, correct fuel selection, and proactive fuel management are essential to ensure lifeboats are ready when they’re needed most: 

Performance when its most critical

In an emergency, a lifeboat engine is not simply a mechanical asset, it is a life-saving system. If the fuel in that system is of poor quality due to degradation, contamination, or simply unsuitable for the operating environment, then the result may be failure to launch, manoeuvre, or sustain operation, when human lives depend on it. Fuel failures in lifeboats onboard Cruise Liners are high-consequence life-safety risk as the engine may be the only power source available during an emergency. It is a key SOLAS (Safety of Life at Sea) requirement that lifeboats should hold sufficient fuel to enable them to run at 6 knots for no less than 25 hours.

The primary consequence of a lifeboat failure is not the commercial  loss, but the potential failure of a safety-critical system during an abandon-ship scenario. Financial, legal and reputational consequences will undoubtedly follow but the immediate risk is to life.

Now with the inclusion of Biofuels and FAME in the marine fuel mix and assuming the same fuel used in the main engines may be used in the emergency systems, how do you verify the operability of the lifeboats in times of crisis?

Fuel grade DMX within the ISO8217 specification is specifically intended for use within emergency equipment. However, since this is not a mandatory requirement, marine gas oil (MGO grade DMA) used for other purposes on board, is often used to fill up lifeboat fuel tanks. This could lead to hazardous outcomes as the DMA grade fuel might not be suitable for its intended use. DMA fuel whilst acceptable for general machinery use, will unlikely provide the same assurance of low-temperature operability, ignition quality, storage reliability, or starting reliability required for emergency craft. The quality of the fuel in the lifeboat tanks may also deteriorate during storage. Hence it is essential to test and ensure that the quality of the fuel being taken into the tanks is ’fit for purpose’ and monitored at regular intervals. DMX fuel should be chosen due to its ability to operate at a lower temperature, superior ignition quality and  improved starting capabilities. However, this fuel only accounts for approximately 1-2% of the global supply, compared to the regular DMA grade.

Failure Modes in Emergency Operations

SOLAS compliance should not be viewed only in terms of carrying the required quality of fuel. The fuel must also remain fit-for-purpose regarding stability, cleanliness and be capable of supporting reliable engine operation throughout the vessel’s operation. Lifeboat failures are rarely a singular dramatic event, rather a chain of events. These are typically caused by degraded fuel, filter blockages or storage issues.  Incorrect handling and storage can result in the ingress of water, which with modern fuels, can promote the growth of filter blocking bacteria rendering the engine inoperable.  So rather than the issue being no fuel, it is more likely to be an issue of fuel that is of poor quality. As lifeboat engines may sit idle for long periods it potentially allows the fuel to degrade, if the correct due care and attention is not paid to this key piece of emergency equipment.

The handling and storage of fuel, coupled with the observance of quality operating procedures can lessen the risk of these failures, but are unlikely to eliminate them completely. However, the failure to follow established procedures can result in issues that are likely to cause catastrophic financial and reputational damage to the cruise line operator.

The most common failure modes in emergency lifeboats can be categorised as follows:

  • Fuel Starvation
  • Contamination
  • Degraded Fuel
  • Blocked Filter/Injectors

Contamination in the engine due to the presence of water, as previously mentioned, can be catastrophic as this can induce corrosion and oxidation, along with promoting microbial growth which results in filter blocking and fuel starvation to the engine.

If an engine fails to start, or runs poorly under load, due to fuel related issues this would likely cause a secondary emergency, compounding the reason the lifeboat was required in the first instance.

The danger with degraded fuel is that the risk is often hidden. A lifeboat may appear available, inspected and compliant, whilst he fuel inside its tank is steadily losing the properties required for reliable emergency operation.

IMO guidelines indicate that inspectors and regulators are increasingly looking at emergency systems for fuel compliance, highlighting its importance in the operation of a vessel.

Seasonal & Regional Fuel Requirements

Often overlooked are the cold flow properties of diesel and biofuels.  While hydrocarbon-based diesel has very good (low temperature) cold flow properties, this is not the case for biofuels, so lifeboats fuelled in the Caribbean for the summer season may be completely inoperable if the vessels are transferred to the Northeast or higher location, for a winter period.

Root Cause Failure Mechanisms

The failure to follow the appropriate standards which result in engine failure can be categorised as follows:

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The Effect of Biofuels on Marine Fuel Quality

In a study recently completed by a major shipping line, blends of biofuels were tested for a wide range of parameters.  The findings were:

Biological growth appeared within the first month, increasing rapidly with exposure to light.

Within 3 months oxidative corrosion started to occur requiring regular monitoring.

46 CFR § 169.837 states:

“(2) The fuel tanks of motor propelled lifeboats have been emptied, and fuel changed once every twelve months.”

Yet the evidence shows fuel stability effectively starts to deteriorate within the first month and can be unusable by month 3.

Prevention Strategy

Fuel testing should be viewed as part of the vessel’s safety assurance programme. It provides evidence that the lifeboat fuel remains fit-for-purpose, not only on the day it was supplied, but throughout storage and across changing operational conditions. A strong housekeeping policy requires a multi-pronged approach to ensure operability in times of crisis; such steps include:

  • Housekeeping – ensuring the fuel system remains closed when not in use to eliminate the ingress of water.
  • Operation – frequently run the engines so that fuel and lubricants are cycled through the units.
  • Testing program – likely to be cheaper and more efficient than changing out the fuel. A well-developed fuel testing program can eliminate the need to change the fuel.
  • Documentation – by recording all the actions taken to protect the emergency systems historic data can be tracked.

Advanced Testing Programs

Due to the importance of these emergency assets several different tests should be considered to ensure the suitability of the fuel.  Testing should include:

  • Cold-Flow properties using Pour Point, Cold Filter plugging Point, Cloud Point
  • Water content for moisture
  • BYF for Microbial testing
  • Acid Number for corrosion tendencies
  • FAME for biofuels content
  • Sulphur for MARPOL Annex VI compliance
  • Visual Appearance
  • Viscosity for flow properties
  • Density
  • Flash Point for SOLAS compliance
  • Cetane Index

Conclusion

It is possible to avoid engine failures, but this can only be achieved with a well-documented and well-followed operating procedure.  Regular fuel sampling and testing along with general good housekeeping techniques will ensure these units are ready go when they are most needed. Once they are seen as an active safety-critical asset rather than a dormant emergency component the value in this process will be realized.

Lifeboat fuel quality is not a housekeeping detail, it is a Safety of Life at Sea issue. Emergency craft must be capable of starting manoeuvring and operating for the required duration whenever called upon. Sub-standard, degraded, contaminated, or unsuitable fuel can compromise that capability and turn an emergency response into a secondary emergency. Regular testing, correct fuel choice, controlled storage and documented fuel management provide the evidence and assurance that lifeboats remain ready when lives depend on them.

 

Photo credit: VPS
Published: 14 July, 2026

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Engine

VPS on precision testing for reliable engine performance: Importance of coolant analysis

Steve Bee of VPS highlighted that coolant analysis can prevent failures through early chemical detection, protect components, maintain performance, plus reduce costs and downtime.

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Steve Bee, Group Marketing and Strategic Projects Director of marine fuels testing company VPS, on Thursday (9 July) highlighted that coolant analysis can prevent failures through early chemical detection, protect components, maintain performance, plus reduce costs and downtime: 

Engine coolants play a critical role in protecting equipment performance, efficiency, and longevity. As cooling system technologies and coolant formulations continue to evolve, regular laboratory analysis has become an essential part of proactive maintenance.

It is widely known that coolants should be managed with the same discipline as other critical fluids, as chemical changes can develop long before visible failures occur.

However, it must be emphasized that coolant analysis is about reliability, not just fluid condition. Modern engines and cooling systems operate under higher thermal loads and tighter tolerances, so even small changes in coolant chemistry can affect corrosion control, heat transfer, and component life.

An effective coolant analysis service should provide operators with an early warning system, helping to identify contamination, degradation, and inhibitor depletion before they become operational failures. The service can be a practical tool for reducing downtime, preventing avoidable repairs, and extending equipment life.

As stated above, many cooling system issues start at the chemical level, long before anything is visible and without analysis you are effectively blind until a failure starts. Through coolant testing, risks such as corrosion, cavitation and scale formation can be detected long before damage occurs.

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As an example, the above images show the damage that can occur when a coolant does not have sufficient concentration to provide adequate protection. This damage can appear as scale formation, reduced heat-transfer efficiency and lower flow rates, which can ultimately lead to corrosion.

Coolants don’t just control temperature, they also chemically protect engines and coolant systems. They effectively prevent corrosion of metals and components, reduce cavitation damage in liners and pumps and help avoid deposit build-up and blockages in heat exchangers. Its true that cooling system damage, is a major source of engine failure.

Coolants must be chemically stable in order to transfer heat effectively, as poor cooling performance directly impacts engine efficiency, fuel consumption and reliability. As a predictive maintenance tool coolant analysis moves operations from emergency repairs to planned maintenance.

Should coolants exhibit degrees of incompatibility, then further issues can arise. Mixing incompatible coolants can cause sludge formation, which will in turn affect coolant circulation, leading to reduced efficiency. In addition incompatible coolants can form sludge or gels, which negatively impacts circulation and heat transfer creating hotspots. Those hotspots can break down lubrication and cause micro-welding between piston and liner surfaces, leading to piston pick-up.

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Historically, many coolants were relatively simple glycol/water formulations supported by inorganic inhibitors such as silicates, phosphates, or borates. However, modern coolants are more sophisticated, including OAT, HOAT, NOAT, POAT, and other specialized blends designed for longer service life and improved protection. This added sophistication creates a need for verification: when systems are topped up, mixed, contaminated, or serviced.

Organic Acid Technology (OAT) coolants, can be formulated with various organic acids such as Sebacate, which is an ester of sebacic acid. Sebacate exhibits low volatility and excellent flexibility at low temperatures. Also tolytriazole can be a component, which is best known as a thermally stable, metal corrosion inhibitor.

So organic acid technology uses organic acids to provide targeted corrosion protection, especially for aluminum and mixed-metal systems. The advantages are, long service life of up to seven years, reduced abrasive deposits, and protection that is generally gentler on seals and components. However, whilst such coolants offer long service life, OAT coolants are not maintenance-free. Its also possible that coolant protection can be slow to establish and performance can be compromised by incorrect mixing, contamination, or loss of inhibitor balance. This is where routine analysis helps verify that the coolant is still doing its job.

Hybrid Organic Acid Technology (HOAT) coolants are newer generation coolants which combine organic acid technology with selected inorganic additives. They aim to provide both long-life protection and faster initial corrosion control through improved heat transfer and cooling performance. This makes them attractive for demanding engines and systems where heat transfer, compatibility, and corrosion control are all critical. The important point is that HOAT chemistry is more complex than traditional coolant chemistry. That complexity can make correct identification, compatibility, and contamination control more difficult. The downsides to HOAT coolants are they are more expensive than traditional coolants, but more concerning is they can be more susceptible to becoming contaminated, affecting their effectiveness and lifespan. Therefore, routine lab testing helps confirm whether the coolant in service still matches the intended formulation and whether the inhibitor package remains effective.

The shipping fleet has numerous sectors and each have various considerations when it comes to the use of coolants:

image 43However, the underlying need for each shipping sector is similar, in that cooling-system reliability supports uptime, safety, and cost control. Deep-sea shipping, offshore and marine services, harbour and coastal operations, cruise and ferry operators, inland waterway vessels, plus port or terminal operators, all have equipment where coolant condition can affect reliability. The commercial message is that coolant analysis can be positioned alongside existing marine fluid management services, making it a logical extension rather than a separate standalone offering.

A typical coolant analysis test slate includes the following tests highlighting what each test parameter detects, their frequency and benefits:

image 43

To take an analogy from Oil Condition Monitoring, Coolant Analysis is effectively a “blood test” for the cooling system.

So in summary, Coolant Analysis can prevent failures through early chemical detection, protect components, maintain performance, plus reduce costs and downtime.

 

Photo credit: VPS
Published: 10 July, 2026

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Lubricants

VPS on longer drains, lower cost: The role of oil analysis of synthetic engine oils

With synthetic engine oils playing an increasingly important role in marine operations, Joe Star of VPS, said the key to unlocking the full value of synthetic lubricants is condition-based oil analysis.

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With synthetic engine oils playing an increasingly important role in modern machinery and marine operations, Joe Star, Strategic Account Manager of marine fuels testing company VPS on Tuesday (7 July), said the key to unlocking the full value of synthetic lubricants is condition-based oil analysis:

A Demanding Environment

Across the United States, many vessels operating offshore and across the country’s inland water ways are powered by high-speed engines. These engines provide one of the most demanding lubrication environments for engine oils to manage.

Engines frequently run at high loads, switching between long periods of continuous operation and shorter stints alternating between idling, standby and high loads during manoeuvring.

Such load changes, temperature variations and extreme conditions, along with the unique operating profile, vessels encounter, place extreme stress on engine oils. This results in leading Equipment Manufacturer’s (OEM’s) typically recommending drain intervals averaging only 250 operating hours. As a consequence, operators regularly assess the use of synthetic based oils, given the performance and commercial benefits that can be realised based upon extended drain intervals.

Whilst synthetic oils offer clear and significant performance advantages, the successful adoption and monetisation of a higher unit cost base product, depends upon implementing a structured and effective oil analysis program. 

The Synthetic Difference

As engine designs, pressures and temperatures have continued to evolve to keep pace with fuel efficiency needs and requirements, a similar situation has evolved across lubricating oils. With higher pressures and temperatures, the stress on the oil has never been greater. Requiring sufficient viscosity, stability, oxidation control and wear protection capabilities, to be prioritised by lubricant formulators.

Synthetic oils are typically granted a longer drain interval by the equipment manufacturer (OEM) and are proven to be able to achieve this due to their high Viscosity Index (VI) capabilities and the largely uniform molecular structure when compared to mineral oils.

In mineral-based oils, molecules can vary in size and shape, leading to inconsistent lubrication and film creation and most importantly can exhibit a quicker breakdown under heat and increased rate of oxidation. This leads to the low 250 operating hour drain interval, typically recommended in operation.

In theory, Synthetic oils have been proven to be able to significantly extend drain intervals to more than 5-6 times the OEM recommended mineral equivalent, with no performance or reliability issues. However, monetising and ensuring that this is completed, requires a mindset shift from scheduled drain intervals to a condition-based approach based upon routine oil analysis. Adjusting and extending drain intervals can mitigate the most common issue which challenges this practice, which is external contamination in the form of fuel dilution or water ingress.

External Contamination and Fuel Dilution

Due to the operational nature of many vessels which use high-speed engines as a primary source of propulsion, fuel dilution and water ingress are some of the most common occurrences of external contamination, limiting the lifespan of lubricants within engines.

Through leveraging VPS’ MyLubes digital application, extracting results reported so far in 2026, it can be seen that approximately 26% of all high-speed engine oil analysis, in which distillate fuels were in operation, were reported as either a caution or an alert against relevant limits.

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70% of the cautions and failures reported were through a combination of Viscosity, Flash Point or Base Number; highlighting the fuel and lubricant interaction; as Viscosity failures covered both elevated and lower Viscosity values. Elevated viscosity being a sign of oxidation and lower viscosity indicating fuel dilution respectively.

Fuel dilution is when fuel enters the crankcase or sump and mixes with the engine oil in the system. Typically, it is distillate fuel (Marine Gas Oil) which is the fuel choice for these engines.

Vessel’s that are more susceptible to fuel dilution are vessels which operate on frequent start-stop cycles, prolonged idling and low-load operation, where operational profiles require short bursts of high load, this can promote fuel ingress into the lubricating oil.

Critically, when looking to maximise lubricant lifespan, VPS data shows that approximately 23% of caution/failed high-speed engine oil analysis results are due to fuel dilution, highlighting that in these instances, either mineral or synthetic based lubricants are not being maximised.

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Fuel dilution has a direct impact on overall lubricant performance, notably:

  • Viscosity reduction, leading to increased metal to metal contact
  • Reduced flashpoint, leading to safety risks and onboard management requirements
  • Accelerated lubricant degradation and corrosion, leading to reduced component lifespan

Mineral and Synthetic based oils are both equally susceptible to fuel dilution occurring. In addition there are financial considerations to manage fuel dilution when Synthetic products are in place, due to the increased unit cost. Ensuring prompt detection and resolution is the most effective tool to effectively minimise the real-world impact of fuel dilution on lubrication strategies.

Monetising a more costly lubricant

Whilst typical mineral based engine oils drain intervals are approximately 250-500 hours, depending upon the engine make and model, synthetic oils have been able to extend drain intervals to over 2000 hours. The benefit to operators is clear on paper, with synthetic oils typically costing 2-3 times more than mineral equivalents. Provided drain intervals are extended beyond 3 times the mineral equivalent, a significant budget saving can be achieved by the operator.

Notably this creates a shift in operating mentality, moving from a time-based approach to a condition-based assessment of oil quality; meaning that a robust oil analysis programme and sampling interval becomes more important, not less.

In addition to providing the most effective early warning with regards to fuel dilution and contamination, a robust Oil Condition Monitoring (OCM) programme is the critical enabler to safely and reliably extending drain intervals with synthetic, or mineral based engine oils.

At a high level, based upon operational experience, VPS’s core recommendations for an effective programme to support extended drains include:

  • Sampling intervals at least twice per drain cycle: Increasing frequency if fuel dilution is observed, or engines are operated at low loads for extended periods
  • In practice, sampling every 200-300 hours is strongly recommended, typically 6-8 times per drain interval for Synthetic lubricants
  • Oil samples to be taken following representative running of the engine
  • Close monitoring of any deviation of trends, through digital platforms
  • Integration of lubricant sampling and data into Maintenance systems
  • Assessment of common limiting factors across fleets and engine types

Lowering Cost

Fundamentally, with high-speed diesel engines being the workhorse of inland waterborne transportation and offshore vessels; lubricants will be a critical part of the total system and subsequent operating cost.

Synthetic based products offer a benefit on paper when compared to mineral oils, however if such products are consumed at the same rate as mineral oils, there is no benefit to expenditure, and more money is spent for the same outcome.

Drain intervals can only be safely extended, and subsequently monetised, through a robust oil analysis programme. In the demanding environment of inland and offshore operations, oil analysis provides more than a measure of lubricant condition; it also delivers valuable insight into the condition of the engine itself. By routinely monitoring oil health, identifying contamination, wear trends and degradation at an early stage, operators can take timely corrective action, protect engine reliability, extend oil life and ultimately reduce operating costs.

 

Photo credit: VPS
Published: 8 July, 2026

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