Business

Intergr8 Fuels: Should the industry worry about decreasing VLSFO viscosity?

Decreasing VLSFO viscosity affects pour points, resulting in wax sludge and other handling difficulties, despite the decline in off-spec VLSFO cases, finds analysis.

Published

6 years ago

March 19, 2020

Admin

[vc_row][vc_column][vc_column_text]Integr8 Fuels, the bunker trading and brokerage arm of Navig8, on Wednesday (18 March) published an article outlining the importance of noting VLSFO viscosity when analysing quality; it was written by Anton Shamray, Senior Research Analyst, and shared with Manifold Times:

VLSFO quality remains a headline IMO2020 topic. As suppliers are getting more experienced at producing VLSFO blends, the proportion of off-spec tests has been declining, although certain quality concerns remain. One of these is the reduction in viscosity, which is due to more distillate blending. This has resulted in vessels being required to adjust age old practices in order to handle and consume the fuel and moreover requires a change in tact when procuring bunkers. The choice of fuel is often limited, however checking quality before buying is as important as ever in order to minimise the risk of claims.

Lower off-specs but watch viscosity and associated issues

Up until recently, the main concern with regard to VLSFO quality was the relatively high number of off-specs, compared with the other grades like HSFO and LSMGO, and particularly on the “sensitive” parameters. However, as seen in Figure 1, this is now changing and the share of VLSFO off-specs has been declining.

On the other hand, it was found that it is not always necessary for a fuel to be off-spec to result in quality issues when it comes to storing and consuming it. As the market adjusts to the IMO2020 switch and pricing makes it favourable, more distillates have recently made their way into the VLSFO blending pool. As suppliers are getting more experienced at producing VLSFO blends the proportion of off spec tests has been declining, although certain quality concerns remain.

Figure 2 shows the increase in the share of distillate based VLSFO blends and the associated reduction in viscosity.

Indeed, viscosity dropped globally from around 160cst in early November to around 100cst by March, a drop of over 35%.

At the same time the share of distillate based VLSFO went up from around 20-25% to 35-40%. The viscosity drop has affected most bunker hubs. For example, viscosity in ARA dropped 30cst by March to 100cst and there was a bigger decrease in Singapore, from 170cst down to 90cst, with an even bigger reduction in Malta, from 150cst to 50cst.

The trend of lowering viscosity in combination with other factors is a cause for concern. Viscosity, density, pour point, aluminium and silicon (ALSI), and sediment potential (TSP) require careful assessment when purchasing and consuming the fuel.

While the majority of ports recorded very few off-spec fuels in January, several locations were particularly affected.

Viscosity and Pour Point

In the past the effective purification of HSFO required a temperature of 98 deg. C for any fuel over 180cst. Given that many VLSFO fuels are now well below this viscosity level, the purifier temperature is adjusted lower to achieve 20-24cst viscosity in the purifier (for example 58 deg. C for a 30cst fuel).

However, the new VLSFOs are more paraffinic (waxy) and with a higher pour point than HSFO. Under reduced purifier temperatures such fuels may tend to produce wax sludge, which could cause serious handling difficulties; it could also potentially affect the efficiency of removing particles such as aluminium and silicon to safe levels.

It is also essential to inject VLSFO into the engine at the correct injection viscosity. For very low viscosity VLSFO the temperature to achieve the correct injection viscosity may well be on, around, or in extreme cases below pour point (at which the fuel no longer flows) and the wax appearance temperature. For example, in order to inject a 5cst and +12 pour point VLSFO.

The trend of lowering viscosity in combination with other factors is cause for concern it has to be heated or cooled to 18 deg. C, which is only 6 deg. C above pour point (recommended min. 10 deg. C above pour point). In trying to rectify this by increasing the injection temperature the corresponding fuel viscosity would fall, in effect leaving an impossibly small window to operate in outside of which poor combustion, deposit formation and loss of energy may occur even though the fuel is fully compliant with the contractual specification.

Therefore, some owners may prefer buying VLSFO with a minimum 30cst viscosity for RMD/E/G/K grades where pour point is limited to 30 deg. C maximum. Alternatively, if the fuel available is less than 30cst viscosity, it is recommended to be sold against the RMA 10 or RMB 30 spec for which there is a much tighter 6 deg. C (0 deg. C for the winter spec) limit on pour point.

Density and Viscosity

High density in combination with low viscosity remains a cause for concern for VLSFOs, similar to HSFO due to the possibility of poor or delayed ignition and combustion which can result in engine damage. This is also reflected in high CCAI readings in such fuels. It is important to remember that the 2005 ISO specification does not offer CCAI protection.

Analysing over 15,000 VLSFO test results it was found that TSP (the ability of the fuel to deposit sediment) appears to trend up with a decrease in viscosity (Figure 3). This may be due to distillate blending and where different VLSFO components (paraffinic, naphthenic, aromatic) are mixed together in a blend.

Moreover, given that the hot filtration test is performed at 100 deg. C the effects of lower purification temperature (due to fuel’s low viscosity) on the purifier with regard to wax formation may not be fully identified.

Overall, VLSFO quality seems to be improving with fewer samples tested offspec, however checking quality before buying is as important as ever. The ISO spec sets the upper limit for most parameters and it was found that even with all parameters on-spec, some VLSFOs may be more problematic than others.

This is not normally the case with HSFO where most parameters vary in a much narrower range and average viscosity, despite dropping slightly recently, is still around 300cst.

When it comes to bunker procurement, Integr8 Fuels provides its customers with full information not only on the price but also on quality, availability and delays. By analysing global trends and changes in quality, Integr8 Fuels are well positioned to help procure quality fuels and minimise the risk of claims.

Source and photo credit: Integr8 Fuels
Published: 19 March, 2020[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_gallery type=”image_grid” images=”9330,9331″ title=”Additional Information”][/vc_column][/vc_row]

Legal

Singapore police arrest eight over alleged illegal MGO transaction off Tuas

SPF says preliminary investigations found that crew members of a Singapore-registered tugboat misappropriated MGO worth about SGD 10,570 without their company’s knowledge and sold it illegally.

Published

3 hours ago

August 14, 2026

Admin

Singapore police arrest eight over alleged illegal MGO transaction off Tuas

The Singapore Police Force (SPF) on Thursday (13 August) said it has arrested eight men, aged between 25 and 54, for their suspected involvement in an illegal transaction of Marine Gas Oil (MGO).

On 13 August 2026 at about 1.05am, officers from the Police Coast Guard (PCG) conducted a check on a Singapore-registered tugboat in the waters off Tuas and discovered that eight crew members were possibly involved in the illegal transaction of MGO.

“Preliminary investigations revealed that the crew members of the tugboats misappropriated MGO valued at about SGD 10,570 (USD 8,258), without their company’s knowledge,” SPF said in a statement.

“The MGO was sold illegally for their personal financial gain.”

The eight crew members will be charged in court on 14 August 2026 with the offence of theft by servant of property in possession of master under Section 381 of the Penal Code 1871 If convicted, they shall be punished with an imprisonment term that may extend to seven years and shall also be liable to fine.

“The Police take a serious view of illegal transaction of MGO in Singapore Territorial Waters and will continue to conduct enforcement and security checks to prevent, deter and detect such illicit activities in Singapore waters,” SPF added.

Photo credit: Singapore Police Force
Published: 14 August, 2026

Port & Regulatory

Gard: Sulphur-related bunker claims rise amid tighter China MSA enforcement

Claims involving excessive sulphur content in marine fuels have been rising, while stricter inspections by the China MSA have heightened the focus on sulphur compliance, particularly in the Bohai Sea.

Published

3 hours ago

August 14, 2026

Admin

Maritime protection and indemnity (P&I) club Gard on Wednesday (12 August) highlighted that claims involving excessive sulphur content in marine fuels have been rising, while stricter inspections by the China MSA have heightened the focus on sulphur compliance, particularly in the Bohai Sea:

Rise in off-spec sulphur claims

Recent claims experience indicates that bunker quality continues to pose a significant operational risk for shipowners. In our earlier review of bunker-related claims during the first five months of 2026, we highlighted a rise in off-specification bunker incidents amid increased pressure on global fuel supply chains following the escalation of the conflict in the Middle East.

Specifically for Sulphur compliance, between January and June 2026, the number of sulphur-related cases increased by more than threefold compared with the same period in 2025. Notably, the number of cases recorded in the first six months of this year has already exceeded the total number reported during the whole of last year by approximately 40%.

While each case is fact-specific, the increase is notable because excessive sulphur content constitutes a MARPOL compliance issue. Unlike many other bunker quality problems, sulphur non-compliance identified through port state inspections can result in vessel delays, enforcement action, and substantial costs associated with debunkering and fuel disposal.

The map below illustrates the geographical distribution of sulphur-related claims recorded during the first six months of 2026, based on the location where the bunkers were stemmed.

Distribution of sulphur related claims

China MSA steps up sulphur compliance enforcement

According to our correspondent, Huatai, on 5 June 2026, the maritime authorities of Tianjin, Hebei, Liaoning and Shandong jointly launched a special campaign on ship pollution prevention and control in the Bohai Sea region. The campaign involves coordinated supervision by local MSA branches across the region and is expected to last nearly five months. It covers major ports and surrounding port areas in the Bohai Sea region, including Tianjin, Tangshan, Qinhuangdao, Huanghua, Jinzhou, Yingkou and Longkou.

While the initiative is broader than bunker sulphur compliance alone, its scope includes inspections relating to air pollution prevention, SOx emissions, fuel compliance and other high-pollution-risk operations. Enforcement measures are expected to comprise onboard inspections, cross-regional enforcement activities, unannounced spot checks and remote monitoring. These efforts will be supported by a combination of UAV patrols, maritime patrol vessels, shore-based monitoring systems and rapid on-site fuel testing.

As a result, vessels trading in the Bohai Sea region may experience increased scrutiny of fuel compliance documentation, fuel sampling records, onboard fuel management procedures, and the handling or disposal of suspected non-compliant fuel.

Documents typically requested by China MSA

Based on our recent experience, including the case discussed above, and subject to the specific requirements of the local MSA office, owners and operators may be requested to provide supporting documentation such as:

Bunker documentation – Bunker Delivery Notes (BDNs), MARPOL fuel sample records, fuel test reports, and relevant fuel quality certificates.
Statutory certificates – including the International Air Pollution Prevention (IAPP) Certificate and International Oil Pollution Prevention (IOPP) Certificate.
Operational records – engine logbooks, deck and navigation logbooks, Oil Record Book entries, and records relating to fuel transfers, storage and consumption.
Sampling documentation – the Master’s statement and any records demonstrating how fuel samples were drawn, sealed, labelled, handled and retained.
Correspondence records – communications with the authorities, bunker suppliers, charterers and other relevant stakeholders.
Fuel disposal records – approved disposal plans, debunkering documentation, receipts and evidence of final disposal, where applicable.

The exact documentation required will depend on the nature of the investigation, the findings of the inspection, and the requirements of the local enforcement authority.

Possible regulatory consequences in China

Under the Air Pollution Prevention and Control Law of the People’s Republic of China, ocean-going vessels are required to use fuel oil meeting atmospheric pollutant control requirements after berthing. Vessels operating within designated emission control areas must also comply with applicable emission standards. Article 106 provides that where vessel fuel oil fails to meet applicable standards or requirements, the competent maritime authorities may impose fines ranging from RMB 10,000 to RMB 100,000. Liability may extend to shipowners, ship operators and ship managers depending upon the circumstances of the case.

Recommendation

Sulphur compliance should be treated as both a fuel quality and regulatory risk. Owners and operators are encouraged to take preventive steps before bunkering, act promptly if non-compliant fuel is suspected, and preserve evidence carefully if an inspection or claim arises. Under amended

Resolution A.1206(34), Appendix 18, 2.1.5, if the BDN shows compliant fuel, but the master has independent test results of the fuel oil sample taken by the ship during the bunkering which indicates non-compliance, the master may document this by notifying the ship’s flag Administration, with copies to:

the competent authority of the relevant port of destination,
the Administration under whose jurisdiction the bunker deliverer is located,
and to the bunker deliverer.

Photo credit: shraga kopstein on Unsplash / Gard
Published: 14 August, 2026

LNG Bunkering

Shell expands LNG bunkering footprint in Spain with Valencia

As one of the region’s key maritime hubs, the company said Valencia expands the options available to shipowners seeking LNG supply along major shipping routes.

Published

3 hours ago

August 14, 2026

Admin

Shell expands LNG bunkering footprint in Spain with Valencia

British oil giant Shell on Thursday (13 August) said Valencia has joined its growing network of bunkering locations, making LNG available as a marine fuel.

The successful completion of the first LNG bunkering operation in Valencia marked an important milestone for Spain and further strengthened Shell’s LNG supply capabilities across the Mediterranean.

In a video shared by the company, bunkering vessel Alice Consulich was shown supplying an undisclosed volume of LNG to the container ship MSC Sabrina.

“As one of the region’s key maritime hubs, Valencia expands the options available to shipowners seeking LNG supply along major shipping routes,” Shell said in a social media post.

Shell said the achievement reflected the strong collaboration across the maritime value chain, including MSC Mediterranean Shipping Company, the Port of Valencia and Fratelli Cosulich Group.

“We look forward to making more LNG bunker deliveries in Valencia and across the Mediterranean as LNG infrastructure and capabilities continue to expand,” the company said.

Photo credit: Shell
Published: 14 August, 2026