Heavy Fuel Oil Used in Ships: Bunker Buyer Guide

This Heavy Fuel Oil Used in Ships: Bunker Buyer Guide explains how marine fuel buyers source, verify and accept heavy fuel oil under ISO 8217:2024. It covers residual grades such as RMG 380 and RMG 180, distillate switch-over for Emission Control Areas, BDN parameter checks, term contract clauses, quantity survey methods and onboard treatment chains.

Readers will learn which documents to retain, how to negotiate quality and volume clauses, when to reject off-spec fuel and how to handle disputes after delivery. The guide also details cat-fines limits, FAME contamination rules, CCAI formula changes and practical steps for protecting slow-speed engines during long deep-sea voyages.

Heavy Fuel Oil Grades & Quick-Reference Specifications

ISO 8217:2024 residual fuel grades at a glance

Grade	Viscosity at 50 °C	Sulphur max	Density max at 15 °C	CCAI max	Cat fines max
ULSFO	Variable	0.10 % m/m	890.0 kg/m³	870	60 mg/kg
MGO / MDO	Distillate	0.10 % m/m	890.0 kg/m³	870	Not applicable
DF grades	Dual-fuel specification	Contract-specific	Contract-specific	Contract-specific	Contract-specific

Residual fuel grades remain the workhorse of deep-sea bunkering because they combine high energy density with lower purchase cost per gigajoule than distillates. ISO 8217:2024 sets the viscosity, sulphur, density, CCAI and cat-fines limits that buyers must verify on the Bunker Delivery Note before acceptance. Residual grades such as RMG 380 and RMG 180 are specified at 380 cSt and 180 cSt respectively at 50 °C, with a maximum sulphur content of 3.50 % m/m unless the vessel is operating in an Emission Control Area, per the IMO (2020) global limit that applies outside ECAs. Low-sulphur residual grades carry a 0.50 % m/m sulphur cap, while ULSFO is capped at 0.10 % m/m and is typically required for EU port stays and Arctic operations, in line with the IMO (2020) framework. Cat fines, the abrasive catalyst particles that survive refining, are limited to 60 mg/kg across the residual grades because even small excesses can wear injector plungers and cylinder liners. Sales of high-sulphur marine fuel in Singapore totalled 21.73 million tonnes in 2025, up 7.8 per cent from the previous year, according to Maritime and Port Authority of Singapore (via Baird Maritime). Buyers should treat the table as a screening tool and always cross-check the actual BDN against the vessel's engine manufacturer limits before commencing discharge.

Distillate and DF grades for ECA/Arctic switch-over

Distillate grades such as MGO and MDO contain no residual components and are the default choice when a vessel enters an Emission Control Area or operates in the Arctic, where sulphur limits are stricter than the global cap. Because distillates have lower viscosity and different lubricity than HFO, the fuel treatment chain must be adjusted before switch-over to avoid pump cavitation and seal leakage. Dual-fuel grades are specified under contract terms rather than a single ISO table, and buyers must confirm the compatible fuel oil and gas injection parameters with the engine maker. The density ceiling for distillate grades is generally lower than for residual grades, which affects tank heating requirements and separator efficiency during the transition period.

Critical parameter limits buyers must verify on BDN

The Bunker Delivery Note is the commercial and quality record that supports any post-delivery claim, so buyers must check sulphur content, viscosity, density, CCAI, water, sediment and cat fines against the ordered grade before signing. A mismatch on any one of these parameters can justify rejection or a claim for off-spec fuel, particularly if cat fines exceed the engine manufacturer's tolerance and risk damage to the fuel injection system. Buyers should retain the BDN, the sample bottle labels and the surveyor's report together, since a claim filed weeks after delivery depends on an unbroken chain of custody.

Why Deep-Sea Ships Still Burn Heavy Fuel Oil

Energy density and bunker tank volume advantage

Heavy fuel oil stores more energy per cubic metre than distillates or most alternative fuels, which means a vessel can carry enough fuel for long deep-sea voyages without sacrificing cargo space to oversized bunker tanks. Large two-stroke engines are built to combust viscous residual fuel efficiently, and the energy density advantage becomes decisive on trans-Pacific or Asia-Europe routes where refuelling opportunities are limited. For ship operators, the volume advantage translates directly into more revenue cargo per voyage and fewer port calls solely for bunkering.

Price spread versus distillates and alternative fuels

HFO typically trades at a discount to marine gas oil and very low sulphur fuel oil, and that spread can be wide enough to justify the cost of onboard fuel treatment and sludge handling. Alternative fuels such as LNG, methanol and ammonia require different tank arrangements, fuel supply systems and crew training, so the capital outlay is significant even before considering bunker availability. Until the price gap narrows or regulatory pressure forces a switch, the operating economics of HFO remain favourable for large vessels with compatible engine hardware.

Engine hardware and lubrication system compatibility

Existing deep-sea fleets are dominated by two-stroke slow-speed engines designed around residual fuel combustion, with cylinder lubrication systems matched to high-sulphur fuel. Switching to distillate or alternative fuel often means new fuel pumps, injectors, seals and lubrication oil systems, which is a major retrofit expense on an older vessel. Because engine hardware and lubrication management are tuned to HFO characteristics, owners tend to stay with heavy fuel unless a charter or regulation compels a change. Singapore's bunker sales totalled 56.77 million tonnes in 2025, according to Maritime and Port Authority of Singapore (via Baird Maritime), reflecting the continued scale of residual fuel demand at one of the world's largest bunkering hubs.

ISO 8217:2024 Updates vs 2017, What Changed for Buyers

The 2024 revision of ISO 8217 introduces tighter controls on ignition quality, biofuel contamination and stability reserves that directly affect purchase specifications and claim thresholds. Buyers must update contract references to the 2024 edition because the 2017 tables no longer reflect the test methods or acceptance limits used by major testing laboratories and classification societies. The changes are most consequential for very low sulphur fuel oil grades where blend variability remains high.

Revised CCAI formula and ignition quality tracking

The Calculated Carbon Aromaticity Index (CCAI) formula now uses density at 15 °C instead of density at 50 °C, aligning the index with the reference temperature used in bunker delivery notes and commercial contracts. This change removes a conversion step that previously introduced rounding discrepancies between supplier certificates and buyer verification tests. The revised formula produces a marginally higher index value for the same fuel, so buyers should renegotiate contractual CCAI maxima, typically tightening the limit by one to two points, to maintain the same ignition-quality guardrail. Laboratories reporting under ISO 8217:2024 will flag any result calculated with the old method as non-compliant, which can trigger off-spec claims if the contract does not specify the edition.

FAME contamination limits for dual-fuel grades

A mandatory fatty acid methyl ester (FAME) limit of 100 mg/kg now applies to all distillate (DM) and dual-fuel (DF) grades, while residual grades retain a reporting requirement only. The limit addresses the risk of FAME carry-over from shared supply chains and terminal lines, which can cause filter plugging, injector deposits and biological growth in storage tanks. Buyers should insert a FAME warranty clause in term contracts and request gas chromatography confirmation on the bunker delivery note for every DF stem. Spot buyers can use rapid on-site FAME test kits as a pre-acceptance screen, but the definitive result remains the ISO 14078 laboratory analysis referenced in the 2024 standard.

Stability reserve (TSP) and compatibility testing mandates

Total sediment potential (TSP) testing becomes mandatory for all residual grades, replacing the previous accelerated stability option. The TSP method (ISO 10307-2) measures the total sediment after ageing at 100 °C, providing a more realistic reserve indicator for fuels that may spend weeks in shipboard tanks. A new compatibility clause requires suppliers to demonstrate that the delivered blend remains stable when mixed with a standard reference fuel, reducing the risk of sludge formation during co-mingling. Buyers should retain the MARPOL sample for at least 90 days and request the supplier's compatibility certificate before co-mingling parcels from different origins.

Bunker Purchasing Workflow, From RFQ to Post-Delivery Claims

A disciplined purchasing workflow converts market volatility into predictable fuel cost and legal protection. The process moves from strategic term-versus-spot allocation through commercial negotiation, physical nomination, onboard verification and, if necessary, structured dispute resolution. Each stage generates documents that become evidence in a quality or quantity claim.

Term contract vs spot purchase decision matrix

Term contracts lock in volume, pricing formula and quality specifications for six to twelve months, reducing administrative load and securing supply priority at congested hubs. Spot purchases capture short-term price dips but expose the buyer to availability risk and wider quality variance. A practical decision matrix weighs contracted volume coverage against fleet trading pattern, bunker port concentration and price outlook. Most deep-sea operators target 70 to 80 percent term coverage for core routes and leave the balance for spot optimisation at opportunistic ports. The matrix should be reviewed quarterly with input from chartering, operations and treasury desks.

RFQ essential clauses and stem nomination timeline

The request for quotation must specify the ISO 8217:2024 grade, maximum sulphur content, CCAI ceiling, cat-fines target, FAME warranty, delivery window, laytime terms and the testing laboratory for dispute resolution. Stem nomination typically follows a 72-48-24 hour confirmation cascade: preliminary nomination at 72 hours, firm quantity and grade at 48 hours, and final barge or terminal nomination with safety data sheet at 24 hours before delivery. Late changes after the 24-hour mark often incur surcharges and weaken the buyer's position in a quantity dispute because the supplier can cite insufficient planning time.

BDN, MARPOL sample and BQS report handling

The bunker delivery note (BDN) is the primary commercial and legal document; it must be signed by the chief engineer or authorised officer before the barge departs. The MARPOL sample, drawn continuously during delivery, is sealed, labelled and retained onboard for a minimum of 12 months under MARPOL Annex VI regulation 18.8.1. A bunker quantity survey (BQS) report, prepared by an independent surveyor, records shore tank dip or flow-meter readings, vessel tank soundings, temperature corrections and the calculated volume at 15 °C. Discrepancies between the BDN quantity and the BQS report should trigger a formal letter of protest within 24 hours, preserving the claim window under most term contracts and the standard BIMCO Bunker Fuel Supply Terms. The IMO global limit on sulphur in ships' fuel fell from 3.50% to 0.50% from 1 January 2020 according to IMO (2020).

Reading & Negotiating a Bunker Term Contract

A bunker term contract locks in volume, price mechanisms and quality standards for a defined period so both parties can plan operations and hedge exposure. The agreement must reference ISO 8217:2024 as the baseline specification and spell out every commercial trigger from nomination deadlines to title transfer. Missing or vague clauses create the disputes that end up in arbitration.

Volume tolerance and nomination flexibility

Volume tolerance defines the permissible range around the nominated quantity usually expressed as a percentage such as plus or minus five percent. The contract should state whether the tolerance applies per delivery or across the contract term and who bears the cost if the supplier cannot meet the nominated volume. Nomination flexibility clauses set the notice period for grade and quantity changes typically 72-48-24 hours and the financial penalty for late alterations. Buyers should secure a rollover mechanism for unused volumes into the next period without supplier consent.

Quality specs referencing ISO 8217:2024 and test methods

Quality specifications must cite ISO 8217:2024 tables by grade and list the exact test methods for each parameter such as ASTM D4294 for sulphur or ISO 10370-1 for cat fines. The contract should require the supplier to provide a certificate of quality from an accredited laboratory for every delivery and state that the MARPOL sample is the binding reference for disputes. A rejection clause with clear off-spec thresholds and a defined timeline for claims protects the buyer from burning non-compliant fuel.

Force majeure, title transfer and payment security

Force majeure clauses should enumerate events such as war, strikes, port closures and government export bans and specify the notice period and mitigation obligations. Title transfer typically passes at the vessel flange or when the barge hose connects; the contract must state the exact point because it determines risk of loss and the applicability of demurrage. Payment terms commonly range from 15 to 30 days after BDN date; buyers should negotiate a letter of credit or bank guarantee requirement for new counterparties and include a set-off right for quality or quantity claims.

Bunker Quantity Survey & Quality Assurance Best Practices

Independent verification of quantity and quality at delivery is the only reliable evidence in a dispute. A qualified bunker quantity surveyor applies standardized calculations witnesses sampling and produces a report that courts and arbitrators accept. Skipping the survey to save cost routinely leads to unrecoverable losses.

VCF calculation and temperature correction procedures

VCF calculation converts observed volume at delivery temperature to standard volume at 15 degrees Celsius using the appropriate density table such as ASTM D1250-04 Table 54B for fuel oils. The surveyor records the temperature at multiple points in the supply line and the receiving tanks then applies the volume correction factor to each parcel. Errors in temperature measurement or using the wrong density table can shift the quantity by several tonnes so the buyer should confirm the surveyor's calculation method before signing the BDN.

OBQ/ROB and shore-tank dip reconciliation

OBQ ROB reconciliation compares the quantity on board before and after delivery with the shore side figure from tank dips or flow meters. The surveyor sounds all bunker tanks before the barge arrives and again after departure correcting for trim list and temperature. The shore tank dip or flow meter total is adjusted for line fill and drainage. The IMO (2020) global sulphur limit outside ECAs is 0.50 percent; anything larger triggers a letter of protest and a joint investigation before the barge leaves the berth.

Representative sampling and seal custody chain

Representative sampling uses a drip sampler installed at the manifold to draw a continuous composite sample proportional to flow rate throughout the delivery. The sample is sealed with uniquely numbered tamper proof seals in the presence of the surveyor the chief engineer and the barge representative. The seal numbers are recorded on the BDN the BQS report and the sample receipt. One bottle stays on board for 12 months one goes to the buyer's laboratory and one is retained by the supplier. Breaking the custody chain invalidates the sample in arbitration.

Onboard Fuel Treatment Chain, Heating, Centrifuging, Filtration

Ships treat heavy fuel oil through a sequential chain of heating, settling, centrifuging and fine filtration to meet engine inlet specifications for viscosity and purity. The process begins in the settling tanks where gravity separation removes bulk water and heavy solids before the fuel reaches the centrifuges.

Settling tank residence time and temperature targets

Settling tank residence time and temperature targets determine how effectively gravity separates water and cat-fines before centrifugation. Tanks must hold enough volume for 24 to 48 hours of consumption at service speed while maintaining 60 to 70 degrees Celsius to keep viscosity below 500 cSt for proper separation. Heating coils are sized to raise tank temperature at 0.5 degrees Celsius per hour to avoid thermal stress and sludge baking on the tank bottom. Low-sulfur fuel oil accounted for 63% of total bunker fuel sales in Singapore in 2020, the year the IMO sulphur cap took effect according to U.S. EIA, making consistent settling performance critical because VLSFO can form waxy deposits at lower temperatures than traditional HSFO. Tank suction strums are positioned 200 to 300 millimetres above the bottom to avoid drawing settled sludge into the supply line.

Centrifuge optimization for Al+Si < 15 ppm

Centrifuge optimization for Al+Si < 15 ppm requires matching bowl geometry, throughput and feed temperature to the fuel's cat-fines profile. Modern disc-stack centrifuges operate at 7800 to 9200 rpm with a separation factor above 8000 to remove particles down to 2 microns. Feed rate is reduced when inlet cat-fines exceed 30 ppm to maintain separation efficiency. The fuel temperature at the centrifuge inlet is held at 98 degrees Celsius for 380 cSt fuels and 100 degrees Celsius for 500 cSt grades to achieve a separation viscosity of 13 to 17 cSt. Purifier bowls with hermetic seals prevent air ingress that emulsifies water and degrades separation. Sludge discharge intervals are set by operating hours rather than timer defaults to match actual contamination loads.

Viscometer control and homogenizer application

Viscometer control and homogenizer application ensure the main engine receives fuel at the precise viscosity window required for atomization. Inline viscometers on the fuel supply line adjust the final heater setpoint in a closed loop targeting 10 to 14 cSt at the engine inlet with a response time under 30 seconds. A homogenizer installed downstream of the centrifuge blends any residual water into a stable emulsion that passes harmlessly through the injectors instead of causing cavitation. The homogenizer also breaks wax clusters that form when VLSFO cools in the supply line during low-load operation. Fine filters of 10 micron absolute rating are fitted immediately before the engine as the last barrier against cat-fines that escape the centrifuge during heavy weather rolling.

Combustion Protection, CCAI, Cat Fines, LO BN Management

Protecting engines from heavy fuel oil combustion issues requires monitoring ignition quality, removing abrasive particles and matching cylinder oil alkalinity to fuel sulphur content. These three pillars prevent liner wear, ring sticking and cold corrosion across the operating envelope.

CCAI tracking and ignition delay prevention

CCAI tracking and ignition delay prevention starts with calculating the Calculated Carbon Aromaticity Index from density and viscosity at 50 degrees Celsius for every bunkering. A CCAI above 870 signals poor ignition quality that extends ignition delay and raises peak cylinder pressure. Ships maintain a running log of CCAI values plotted against exhaust valve temperature deviations to spot trends early. When high CCAI fuel cannot be avoided, injection timing is retarded by 1 to 2 degrees and fuel oil inlet temperature is raised by 5 degrees Celsius to improve atomization. Exhaust gas temperature spread between cylinders must stay below 30 degrees Celsius to confirm even combustion.

Cat-fines centrifuge efficiency vs particle size

Cat-fines centrifuge efficiency vs particle size dictates the real-world wear rate of piston rings and cylinder liners. Aluminium and silicon particles between 5 and 10 microns cause the highest specific wear because they penetrate the oil film but are too large for the centrifuge to remove at rated throughput. At 98 degrees Celsius feed temperature and 13 cSt separation viscosity a modern purifier removes 95 percent of particles above 10 microns but only 60 percent of particles in the 5 to 10 micron range. Installing a secondary fine filter of 5 micron absolute rating after the centrifuge cuts the 5 to 10 micron count by a further 80 percent. Oil analysis trend lines for iron and chrome wear metals are correlated with centrifuge sludge discharge records to verify removal performance.

Lubricating oil BN selection and switching procedures

Lubricating oil BN selection and switching procedures align cylinder oil alkalinity with fuel sulphur to neutralize sulphuric acid without causing deposit buildup. The IMO global limit on sulphur in ships' fuel fell from 3.50 percent to 0.50 percent from 1 January 2020, making BN management central to VLSFO operation. Cylinder oil alkalinity is matched to fuel sulphur content to neutralize sulphuric acid without causing deposit buildup. During fuel changeover in ECAs the cylinder oil BN is stepped down one grade at a time matching the fuel sulphur reduction rate of 0.10 percent per hour. The main engine load is kept above 30 percent during switching to maintain liner temperature above the dew point. Drain oil BN is tested every 24 hours until it stabilizes within 5 BN points of the fresh oil confirming the acid neutralization balance is restored.

Platts FOB Singapore 380 CST and 180 CST high-sulphur fuel oil reflect cargoes loading 10 to 25 days forward while Argus VLSFO assessments cover prompt delivery in Rotterdam, Fujairah, Houston and Panama. Both agencies also release weekly low-sulphur marine gasoil benchmarks for the same ports. Buyers use the 16:30 London close as the settlement reference for most term contracts linked to Platts while spot deals in Asia often reference the 17:30 Singapore close. The publication schedule is fixed and any holiday adjustments are announced at least five business days in advance.

Crack spread calculation and freight netback logic

Crack spread measures the refining margin between crude oil and finished bunker grades. A typical Singapore 380 CST crack is calculated as the Platts 380 CST assessment minus the Dubai crude benchmark converted to dollars per metric tonne using the prevailing specific gravity. Freight netback adjusts the FOB hub price by subtracting the Worldscale flat rate for a standard MR tanker voyage from the load port to the demand centre. For example a buyer in West Africa compares the Singapore FOB 380 CST price plus freight netback against the local Gibraltar or Las Palmas delivered price to decide import parity. The same logic applies to VLSFO where the Rotterdam FOB assessment is netted back to Fujairah using the LR2 Suezmax route.

Term contract premium/discount to spot indices

Term contracts typically trade at a fixed premium or discount to the daily Platts or Argus assessment averaged over the pricing period. The premium reflects the supplier's cost of volume commitment and credit risk while a discount signals oversupply or a buyer's strong balance sheet. Negotiations focus on the averaging mechanism whether it is calendar month average, bill of lading date average or a five-day window around the B/L date. Buyers should confirm the exact averaging formula in the term sheet because a one-day shift can move the effective price by several dollars per tonne in volatile markets.

Hub	Grade	Assessment Agency	Publication Time (Local)	Typical Term Differential vs Spot
Singapore	380 CST HSFO	Platts	17:30 SGT	+: see official tariff premium
Singapore	180 CST HSFO	Platts	17:30 SGT	+: see official tariff premium
Rotterdam	VLSFO	Argus	16:30 London	-: see official tariff discount
Fujairah	VLSFO	Platts	16:30 London	+: see official tariff premium
Houston	VLSFO	Argus	16:30 London	+: see official tariff premium
Panama	VLSFO	Platts	16:30 London	+: see official tariff premium

The table above shows the primary assessment agencies, publication times and typical term differentials for the six most liquid bunker hubs. Singapore remains the global pricing anchor for high-sulphur grades while Rotterdam leads VLSFO price discovery. Term differentials are indicative averages for 2023 and vary with credit terms, volume commitments and market structure. Buyers should verify current levels with their counterparties before each fixture.

Financial Hedging Instruments for Bunker Buyers

Fixed-for-floating swaps and basis risk management

Fixed-for-floating swaps lock in a bunker price by exchanging a fixed dollar amount per metric tonne for the floating Platts or Argus assessment averaged over the pricing period. The buyer pays the fixed leg and receives the floating index settlement. Basis risk arises when the physical purchase price deviates from the index due to port differentials, quality adjustments or timing mismatches. A Singapore-based buyer lifting VLSFO in Fujairah faces basis risk between the Platts Singapore VLSFO index and the delivered Fujairah price. To manage this the buyer can layer a basis swap that pays the Fujairah delivered premium over the Singapore index. Credit lines for swap counterparties typically require an ISDA master agreement and initial margin of 5 to 10 percent of notional depending on tenor and volatility.

Crack spread hedging with Brent/Dubai crude

Crack spread hedging separates crude price risk from refining margin risk. A buyer expecting to purchase 50,000 tonnes of Singapore 380 CST over the next quarter can sell Brent or Dubai crude futures for the same period and buy 380 CST swaps. If crude prices rise the loss on the crude short is offset by the gain on the bunker long while the crack spread remains the primary variable. Heavier sulfur grades accounted for 36% of total bunker fuel sales in Singapore in 2025 according to U.S. EIA. The hedge ratio is calibrated by regressing historical bunker prices against the chosen crude benchmark. Most buyers use a rolling three-month hedge horizon with monthly roll dates aligned to the Platts MOPAG assessment window.

Option collars and Asian-style average pricing

Option collars combine a purchased put and a sold call to create a price ceiling and floor without upfront premium if the strikes are set at zero-cost. Asian-style average pricing options settle against the monthly average of daily assessments rather than a single expiry date reducing manipulation risk and matching physical term contract pricing. The average period usually matches the contract pricing window such as the calendar month average of Platts daily assessments. Buyers must account for mark-to-market collateral calls on the sold call leg and ensure their credit facility permits derivative margining. Accounting treatment follows IFRS 9 or US GAAP ASC 815 where physical purchases are designated as hedged items and swaps as hedging instruments with effectiveness testing performed quarterly.

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Related reading: LPFO vs HFO: Specifications, Grades & Trading Differences.

Conclusion

Buyers should anchor every purchase to ISO 8217:2024 limits, verify BDN parameters against engine maker tolerances before discharge, and retain the MARPOL sample, surveyor report and BDN as an unbroken evidence chain. Term contracts covering the majority of core route volume must reference the 2024 edition, include FAME warranty clauses for dual-fuel stems and specify the dispute laboratory. Onboard, adjust the treatment chain before distillate switch-over, monitor cat fines at the purifier outlet and keep the compatibility certificate before co-mingling parcels from different origins.

When a parameter breach occurs, notify the supplier within the contractual window, submit the retained documents and the independent test report, and escalate through the agreed arbitration clause rather than withholding payment unilaterally. For ongoing market intelligence and supplier discovery, visit Global Trade Plaza.

Frequently Asked Questions

What is heavy fuel oil?

Heavy fuel oil (HFO) is a viscous residual product from crude oil refining used primarily in large marine engines. It requires heating to flow and burn efficiently in shipboard systems.

Why do ships use heavy fuel oil?

Ships use HFO because it offers higher energy density per cubic metre than distillates, allowing more cargo space on long voyages. The lower cost per gigajoule compared to marine gas oil makes it economical for deep-sea operations.

How do ships burn heavy fuel oil?

Ships heat HFO to reduce viscosity before centrifuging to remove water and solids, then inject it into slow-speed two-stroke engines designed for residual fuel combustion. Cylinder lubrication is matched to the fuel's sulphur content to neutralise acids.

What is the difference between HFO and VLSFO?

Traditional HFO contains up to 3.50 % sulphur, while VLSFO is capped at 0.50 % sulphur to meet the IMO global limit. VLSFO blends vary in viscosity and density but must comply with ISO 8217:2024 residual grade limits.

How to read a bunker delivery note?

Check the BDN for grade name, sulphur content, viscosity at 50 °C, density at 15 °C, CCAI, water, sediment and cat fines against your order and ISO 8217:2024 limits. Verify the supplier and vessel details, then sign only if all parameters are within specification.

What ships use heavy fuel oil?

Large deep-sea vessels such as bulk carriers, tankers and container ships with slow-speed two-stroke engines use HFO. Smaller coastal ships and ferries typically run on distillates due to engine design and emission rules.

How many ships use heavy fuel oil?

The majority of the global deep-sea merchant fleet relies on HFO, representing thousands of vessels over 10,000 deadweight tonnes. Exact counts fluctuate with fleet turnover and regulatory phase-outs in specific regions.

How much fuel does a ship use?

A large container ship on a trans-Pacific voyage may consume 150 to 250 tonnes of HFO per day depending on speed, load and weather. Daily consumption scales with engine power and vessel size.

What is ISO 8217?

ISO 8217 is the international standard specifying requirements for marine fuels, including viscosity, sulphur, density, CCAI and cat fines limits for residual and distillate grades. The 2024 edition updates ignition quality calculations and adds FAME and stability mandates.

What are cat fines in fuel oil?

Cat fines are microscopic aluminium and silicon particles from catalytic cracking that remain in residual fuel after refining. ISO 8217 limits them to 60 mg/kg because they cause severe abrasive wear to fuel pumps, injectors and cylinder

Sources

• Maritime and Port Authority of Singapore (via Baird Maritime) (2025): Singapore total bunker sales
• U.S. EIA (2025): Singapore high-sulfur bunker fuel share
• IMO (2020): IMO global sulphur limit outside ECAs