Extended Operational and Trade Vocabulary

Marine Fuels, Bunkering, and Alternative Fuels glossary

Vocabulary of marine fuels and bunkering: abatement technologies such as scrubbers and SCR, ISO 8217 quality parameters like acid number, fuel additive packages, major bunker hubs, and the alternative fuels including LNG, methanol, ammonia, hydrogen and biofuels adopted to meet MARPOL Annex VI limits and reduce greenhouse-gas emissions.

259 defined terms.

Showing 250 on this page (page 1 of 2).

A

Abatement technology: Any onboard system (such as a scrubber or SCR) that reduces regulated emissions from marine fuel combustion to meet MARPOL Annex VI limits.
Acid number: Milligrams of KOH required to neutralize the acids in one gram of oil; measured per ASTM D664 for lubricants.
Additives (fuel): Chemical packages (combustion improvers, ash modifiers, asphaltene dispersants, biocides) blended into marine fuels to address stability, ignition, or microbial issues.
Algeciras: Spanish port at the Strait of Gibraltar hosting the busiest Mediterranean ferry corridor to Tangier Med and Ceuta.
Alternative Fuel: Fuel other than conventional fuel oil, including LNG, methanol, ammonia, and hydrogen.
Ammonia (NH3) as fuel: A carbon-free fuel under active pilot for two-stroke main engines, with key challenges around toxicity, NOx slip, and bunkering safety.
Ammonia bunkering pilot: Ship-to-ship and shore-to-ship trials being conducted in Singapore, Pilbara, and the Port of Rotterdam ahead of commercial NH3 supply.
Anti-foam additive: A silicone-based additive added at the refinery or during bunkering to prevent foaming of distillate fuels during tank fill.
API Gravity: American Petroleum Institute density scale; higher API = lighter crude.
ARA: Amsterdam-Rotterdam-Antwerp refining and bunkering range, the world's second largest bunker hub by volume after Singapore at roughly 10 to 12 million tonnes per year.
Aromaticity: Measure of aromatic hydrocarbon content in residual fuels, correlated with ignition delay and quantified through the CCAI index in ISO 8217.
Ash content: Inorganic residue after combustion of a fuel sample, measured per ISO 6245, capped at 0.100% m/m for most residual grades.
ASTM D4294: Energy-dispersive X-ray fluorescence (EDXRF) test for sulphur in petroleum products.
ASTM D7112: Spot test method for determining compatibility and stability of residual fuel blends using a spot on filter paper.
ASTM D7619: Particle count by optical microscopy for cat fines and other solids in middle distillates and residual fuel.
Auxiliary engine: Medium-speed engine driving a generator.
Avenir Aspiration: LNG carrier and bunker vessel in the Avenir LNG fleet.
Avenir LNG: Small-scale LNG shipping and supply company majority owned by Stolt-Nielsen and Golar LNG, operating LNG bunker vessels including Avenir Achievement.

B

B100: Marine biofuel grade composed of 100 percent FAME or HVO, used in trials and select coastal services.
B24: Bunker blend of approximately 24 percent biofuel with VLSFO base, commonly sold as VLSFO-B24 in Singapore and Rotterdam.
B30: Blend of about 30 percent biofuel with conventional MGO or VLSFO used in commercial marine bunkering.
Back-end loaded sample: Improper sampling that draws fuel only at the end of delivery; ISO 13739 requires continuous drip sampling throughout the bunker transfer.
Baltic Sea ECA (NOx): A NOx Emission Control Area in force from 1 January 2021 requiring Tier III compliance for keels laid on or after that date.
Baltic Sea ECA (SOx): A SOx Emission Control Area in force since 2006 with a 0.10% m/m sulfur cap inside the area.
Bareboat: Not a fuel term itself, but relevant since bareboat charterers typically procure their own bunkers under standard time-charter logic adapted to bareboat clauses.
Barge (bunker barge): A vessel or dumb craft that delivers bunkers to a ship at anchor or berth, common at Singapore, Rotterdam, and Fujairah.
BDN (Bunker Delivery Note): Mandatory document under MARPOL Annex VI Reg 18 listing fuel particulars, retained on board for three years.
BDN 12-month retention: Regulation 18 requirement that the BDN and the associated MARPOL sample be retained onboard for at least three years and twelve months respectively (sample is 12 months minimum).
BIMCO Bunker Terms: A suite of standard bunker contract terms (Bunker Terms 2018, Bunker Non-Lien Clause) published by BIMCO for use in supply contracts.
Biocide: Chemical substance that controls harmful organisms, used in antifouling paints and certain BWMS.
Biodiesel (FAME): Fatty acid methyl ester; carried in dedicated or well-cleaned product tanks.
Biofuel: Liquid or gaseous fuel from biomass; covered by ISCC EU or RED II certification for FuelEU.
Biomethane (bio-LNG): Methane produced from anaerobic digestion of organic waste, liquefied to bio-LNG and considered carbon-neutral on a well-to-wake basis with ISCC certification.
Black Products: Heavy refined oils such as fuel oil, bunker, asphalt.
Blend: A mixed fuel produced by combining residual and distillate streams (or biofuel streams) to meet a target viscosity and sulfur specification.
BP Marine: Marine lubricants division of BP that markets the Energol and, through Castrol Marine, Cyltech and CDX product families.
Brassavola: 12,000 m3 LNG bunker vessel operated by Pavilion Energy in Singapore from 2021.
Bunker: Marine fuel oil used by container vessels.
Bunker barge meter: A mass flow meter (Coriolis) used on bunker barges, mandatory in Singapore since 1 January 2017 for distillates and 1 July 2017 for residuals.
Bunker Hold: A common industry workflow term for the operational pause when fuel quality is in dispute; also a brand name for bunker management software.
Bunker Holding: Danish parent group based in Middelfart owning Bunker One, Dan Bunkering, Unicorn Petroleum, and KPI Bridge Oil, marketed as the world's largest bunker company by volume.
Bunker quality dispute: A claim arising from off-spec fuel where the buyer asserts deviation from ISO 8217 or contractual specification.
Bunker receipt (BRN): An informal acknowledgement of delivery used alongside the formal BDN.
Bunker requisition: The ship's internal order document specifying grade, quantity, and delivery window for the next bunker stem.
Bureau Veritas VeriFuel: The marine fuel testing and advisory arm of Bureau Veritas, offering ISO 8217 analysis and bunker quantity surveys.
Busan: The headquarters city of the Korea Hydrographic and Oceanographic Agency.

C

Calorific value: Heat released on complete combustion of a unit mass of fuel, reported as gross or net.
CARB (California Air Resources Board): The state regulator whose Ocean-Going Vessel Fuel Rule required distillate use within 24 nm of the California coast before being superseded by the North American ECA.
Cat fines: Aluminosilicate catalyst particles from refinery FCC units, abrasive to liners, rings, and fuel pumps.
CCAI (Calculated Carbon Aromaticity Index): Ignition quality indicator for marine fuels.
CCS (Carbon Capture and Storage): Capture of CO2 from a source followed by permanent geological storage.
Chevron Marine Products: Marine lubricants division of Chevron that markets the Taro and Veritas families.
CII (Carbon Intensity Indicator): IMO operational efficiency rating influenced by fuel type and consumption.
CIMAC: International Council on Combustion Engines, sets standards and round-table papers.
Closed-loop scrubber: Exhaust gas cleaning system using a recirculated alkaline wash with onboard residue handling.
Cold filter plugging point (CFPP): Lowest temperature at which a measured volume of distillate passes through a standardized filter, per EN 116.
Cold flow properties: Combined behavior of distillate fuels at low temperatures, including pour, cloud, and CFPP.
Combined sample: The representative MARPOL sample assembled from a continuous drip during bunker delivery, sealed in the presence of the supplier and the master.
Compatibility: Ability of two fuels to be mixed without precipitation of asphaltenes, assessed by spot test (ASTM D4740).
Coralius: 5,800 cubic meter LNG bunker vessel delivered in 2017 and operated in Northern European waters.
Coriolis flow meter: Mass flow instrument used on grout mixing skids during monopile and transition piece grouting.
Cross-contamination: Mixing of incompatible fuels in barge, bunker line, or ship tanks leading to sludge, blocked filters, or engine damage.
CST (centistokes): A unit of kinematic viscosity (mm2/s) used for marine fuel grading; 380 CST and 180 CST at 50 degrees C are common residual grades.
Cylinder oil: High-BN lubricant feeding the cylinder liners of two-stroke crosshead engines.

D

Dan Bunkering: Bunker trading subsidiary of Bunker Holding, the world's largest bunker broker by volume.
DCS (Data Collection System): The IMO regulation requiring ships above 5,000 gross tonnage to report annual fuel oil consumption and related data to the Organization through their flag.
De-bunker: To remove fuel previously loaded onto a vessel, typically for off-spec product or compatibility reasons.
Density at 15 degrees C: Reference density of marine fuels expressed in kg/m3, determined per ISO 12185 and used in mass-to-volume conversion.
DF grade (distillate biofuel): Distillate marine fuels containing up to 7% FAME under ISO 8217:2017 (grades DFA, DFZ, DFB).
Differential pressure: dP, monitored across filters and coolers to indicate fouling.
DMA (ISO 8217): A distillate marine grade with a maximum viscosity of 6.000 mm2/s at 40 degrees C and 1.50% m/m max sulfur (general grade).
DMB (ISO 8217): A distillate marine grade with a maximum viscosity of 11.00 mm2/s at 40 degrees C allowing trace residual content.
DMX (ISO 8217): A premium distillate intended primarily for use in lifeboats and emergency applications, with a low pour point and a flash point above 43 degrees C.
DMZ (ISO 8217): A distillate marine grade similar to DMA but with a higher minimum viscosity of 3.00 mm2/s at 40 degrees C, suited to engines requiring higher viscosity for injector lubrication.
DNV VPS: See VPS.
Drip sample: Sample continuously drawn at constant rate during bunker transfer via a sampling cock at the ship manifold.
Dual-fuel engine: Engine running on both liquid and gaseous fuels (e.g., WinGD X-DF).

E

E-Fuel: Synthetic fuel produced from renewable electricity and CO2 or N2.
ECA (Emission Control Area): Designated sea area with stricter sulphur (0.10% m/m) and NOx limits under MARPOL Annex VI.
ECA crossing log: A bridge or engine room record documenting the time, position, fuel grade in use, and tank quantities at the entry to and exit from an ECA.
ECA-NOx: The Tier III NOx requirement applicable to keels laid in or after specified dates in the North America ECA (2016) and Baltic and North Sea ECAs (2021).
ECA-SOx: The 0.10% m/m sulfur cap in force in the Baltic, North Sea, North American, US Caribbean, and (from 1 May 2025) Mediterranean Emission Control Areas.
Energy density: Heat released per unit mass or per unit volume of fuel, central to bunker economics.
Engie Zeebrugge: 5,000 cubic meter LNG bunker vessel delivered in 2017 and based at Zeebrugge, Belgium.
Engine fuel system flush: The procedure of running distillate through the high-pressure fuel system before maintenance or before a long lay-up.
Equivalent compliance: Provision under Regulation A-5 for ships engaged on short international voyages such as pleasure craft and SAR.
EU ETS Maritime: Extension of the EU Emissions Trading System to shipping under Directive 2023/959; applies from 1 January 2024 with phased surrender of 40% in 2024, 70% in 2025, and 100% from 2026.
EU FuelEU Maritime: An EU regulation in force from 1 January 2025 setting a declining GHG intensity limit on energy used by ships above 5,000 GT on EU-related voyages.
EU MRV: EU Regulation 2015/757 on monitoring, reporting, and verification of CO2 emissions from shipping.
ExxonMobil Marine: Marine fuels and lubricants business of ExxonMobil that markets the Mobilgard family.

F

FAME: See Biodiesel.
Fenders: Pneumatic or foam fenders rigged between a receiving ship and a bunker barge during STS bunkering to prevent hull damage.
Final boiling point: The highest temperature at which the last drop of fuel distills off in an ASTM D86 distillation test, relevant for distillate marine fuels.
Fishbone (debate): Industry slang referring to detailed sample chain-of-custody disputes in off-spec bunker claims.
Flash point: Lowest temperature at which fuel vapor ignites with a pilot flame; minimum 60 C for SOLAS marine fuels (Pensky-Martens closed cup, ISO 2719).
Flowmeter compounding: The use of multiple Coriolis meters and aggregating logic in bunker barges to ensure accurate mass measurement under varied flow conditions.
FOBAS: Lloyd's Register Fuel Oil Bunker Analysis and Advisory Service.
Free water: Visible water phase distinct from fuel, settling at tank bottoms.
Fuel changeover procedure: Documented stepwise procedure to switch fuel grades within engine and boiler limits.
Fuel Oil: Defined under MARPOL Annex VI Regulation 2.
Fuel oil treatment plant: Combined heating, separating, and filtering installation upstream of the fuel injection system.
Fuel Sample: Pre-refuel jar sample checked for water, sediment, and color contamination.
Fuel-mix penalty: A FuelEU Maritime concept where exceeding the GHG intensity limit triggers a financial penalty multiplied by a non-compliance factor.
Fujairah: UAE east-coast bunker hub outside the Strait of Hormuz, ranked third globally by volume after Singapore and ARA at roughly 7 to 9 million tonnes per year.

G

Gas Agility: An 18,600 m3 LNG bunker vessel operated by Total Marine Fuels Global Solutions out of Rotterdam since 2020, one of the world's largest LBVs.
Gas carrier (LNGC): A purpose-built LNG carrier; some are used as floating storage and reloading units for LNG bunker supply.
Gas Vitality: An 18,600 m3 LNG bunker vessel operated by TotalEnergies serving the Mediterranean from Marseille-Fos from 2021.
GHG Intensity: Well-to-wake greenhouse gas emission intensity used in FuelEU Maritime accounting.
Glander International Bunkering: Bunker trader founded in 1989 with offices in Stamford, Dubai, Singapore, and Hamburg, owned by the Wonsild family.
Green Ammonia: Ammonia produced from renewable hydrogen via the Haber-Bosch process.
Green Methanol: Methanol produced from renewable feedstocks.

H

HFO (Heavy Fuel Oil): A general term for residual marine fuel typically with viscosity of 180 or 380 cSt at 50 degrees C; in the global cap era HFO usually denotes HSFO at greater than 0.50% sulfur.
HHV (Higher Heating Value): The gross calorific value of a fuel including the latent heat of water vapor produced during combustion.
High pressure dual-fuel (HPDF): Engine category including MAN ME-GI; reduces methane slip versus low-pressure designs.
Hong Kong bunker hub: A long-established bunker port supplying VLSFO and MGO in South China.
Houston bunker hub: A US Gulf bunker market serving the Houston Ship Channel, with several VLSFO and MGO suppliers.
HSFO (High Sulfur Fuel Oil): Residual fuel oil with sulfur content above the 0.50% global cap, generally only usable with an approved scrubber.
HVO (Hydrotreated Vegetable Oil): Renewable diesel produced by hydroprocessing fats and oils, fully compatible with conventional distillate systems.
Hybrid Scrubber: EGCS capable of switching between open-loop and closed-loop modes.
Hydrogen (H2): A zero-carbon fuel under early-stage maritime adoption, mainly for fuel cells, with cryogenic and pressurized storage challenges.

I

IFO 180: Intermediate Fuel Oil with nominal viscosity 180 cSt at 50 C, residual blend.
IFO 380: Intermediate Fuel Oil with nominal viscosity 380 cSt at 50 C, historically the dominant residual grade.
IGF Code: International Code of Safety for Ships Using Gases or Other Low-Flashpoint Fuels.
Ignition quality: Combined behavior of ignition delay and combustion progression, indicated by CCAI for residuals and cetane for distillates.
IMO 2020: 0.50% sulfur cap on marine fuels; not a GHG measure but driving fuel mix changes.
In-line blending: Mixing components during transfer rather than in a static tank.
In-tank blending: Blending two fuels by loading them into the same ship tank; widely discouraged due to compatibility risk.
Intertek ShipCare: Intertek's marine fuel testing service offering ISO 8217 analysis and bunker quantity surveys.
ISCC certification: International Sustainability and Carbon Certification, a chain-of-custody scheme used to evidence sustainable biofuel feedstocks for marine biofuels.
ISO 13739: The international standard procedure for the transfer of bunkers, including continuous drip sampling and BDN content.
ISO 4259: Statistical interpretation of test data for petroleum products, used to assess spec compliance with precision.
ISO 8217: International standard for marine fuel oil specifications.
ISO 8217:2017: Sixth edition with renumbered distillate grades, DFA/DFZ/DFB FAME-containing grades, and updated stability/cleanliness requirements.
ISO 8217:2024: Specification of petroleum products for fuels for marine diesel engines, including grades incorporating biofuel content.

J

Jamnagar: Indian port city in Gujarat with significant LPG import and refining infrastructure, served by VLGCs and MGCs.
Jet A-1: Aviation kerosene; cleanliness paramount.

K

Kairos: 7,500 cubic meter LNG bunker vessel operated by Nauticor for Northern European fueling services.
Karl Fischer titration: Coulometric or volumetric water determination per ISO 12937 or ASTM D6304.
Kinematic viscosity: Ratio of dynamic viscosity to density, expressed in cSt; ISO 8217 specifies viscosity at 50 C for residuals and at 40 C for distillates.

L

Las Palmas: Canary Islands bunker hub for Atlantic crossings, supplied by Repsol, Cepsa, Petrologis Canarias, and Ducar.
LBV (LNG Bunker Vessel): A purpose-built or converted vessel that delivers LNG bunkers ship-to-ship to LNG-fueled ships.
LCV (Lower Calorific Value): The net calorific value of a fuel, excluding the latent heat of water vapor; used in FuelEU Maritime energy calculations.
Lloyd's Register FOBAS: Fuel oil testing and advisory service operated by Lloyd's Register from facilities in Singapore and the United Kingdom.
LNG (Liquefied Natural Gas): Methane-dominant fuel liquefied at approximately minus 162 C; typical WtW reduction of 15 to 20 percent versus HFO is offset by methane slip.
LNG Bunkering: Process of supplying liquefied natural gas as marine fuel.
Long Beach: California cruise homeport hosting the permanently moored Queen Mary and Carnival's Carnival Firenze and Carnival Panorama.
Lower flammability limit (LFL): The minimum vapor concentration that will burn in air; for methane it is around 5% v/v, a key safety parameter for LNG and methanol bunkering.
LPG (Liquefied Petroleum Gas): Propane or butane used as a marine fuel, primarily on LPG carriers with dual-fuel engines.
LSFO: Low Sulphur Fuel Oil, generic term for residuals at or below 1.00% m/m sulphur.
LSMGO: Low-sulfur marine gas oil, a distillate marine fuel with sulfur content of 0.10% m/m or below, used in ECAs and EU ports.

M

MARPOL Annex VI: Air pollution and energy-efficiency annex.
MARPOL Annex VI Reg 14: Sulphur content of fuel oil global cap (0.50% m/m) and ECA cap (0.10% m/m).
MARPOL Annex VI Reg 18: Fuel oil availability and quality, BDN, sampling, and FONAR.
MARPOL Sample: Sealed 400 ml minimum sample drawn during 100 percent of delivery, retained on board 12 months for verification per MEPC.182(59).
Mass flow meter: MFM, custody transfer meter required for bunkering in Singapore and other ports.
MDO (Marine Diesel Oil): A distillate or distillate-residual blend marine fuel, generally corresponding to ISO 8217 DMB grade.
Mediterranean SOx ECA: An IMO-designated SOx ECA in force from 1 May 2025 applying the 0.10% m/m sulfur cap across the Mediterranean Sea.
Mercuria: A Swiss-based global commodity trader active in marine bunker trading and physical supply.
Methane number (MN): A metric for the knock resistance of gaseous fuels, broadly analogous to octane number, with LNG values typically 70 to 90.
Methane Slip: Unburned methane emissions from dual-fuel LNG engines.
Methanol (CH3OH): Liquid fuel with low flashpoint; gray, blue, bio, and e-pathways exist.
Methanol Bunkering: Supply of methanol as marine fuel.
MGO (Marine Gas Oil): Distillate marine fuel meeting ISO 8217 grades DMA/DMZ.
Micro carbon residue (MCR): The carbon residue left after pyrolytic decomposition of a fuel sample (per ASTM D4530 or ISO 10370), an indicator of combustion deposit tendency.
Minerva Bunkering: Geneva based bunker trader and physical supplier formed in 2018 from the spin off of Aegean Marine Petroleum operations.
Monjasa: Danish bunker supplier headquartered in Fredericia operating a fleet of more than 30 bunker tankers across West Africa, Panama, Houston, ARA, Fujairah, and the Mediterranean.
MSAR (Multiphase Superfine Atomized Residue): A water-in-oil emulsion fuel technology, occasionally trialled but not widely adopted.

N

NaOH (caustic soda): The alkaline reagent used to neutralize wash water in closed-loop scrubbers.
NETL: The US National Energy Technology Laboratory, occasionally cited in marine fuel lifecycle GHG references.
New Orleans: A US Gulf bunker market on the Mississippi River.
North American ECA: Designated under MARPOL Annex VI.
North Sea NOx ECA: A NOx ECA in force from 1 January 2021 for ships keel-laid on or after that date.
North Sea SOx ECA: A SOx ECA in force since 2007 with a 0.10% m/m sulfur cap.
NOx Technical Code 2008: Mandatory under MARPOL Annex VI.
NOx Tier I: Applicable to engines on ships with keels laid on or after 1 January 2000 and before 1 January 2011.
NOx Tier II: Applicable to engines on ships with keels laid on or after 1 January 2011, globally.
NOx Tier III: MARPOL Annex VI NOx limit applying in NOx ECAs; relevant for SCR-equipped alt-fuel engines.

O

Off-spec Fuel: Marine fuel found not to meet declared sulfur content on testing.
Open loop scrubber: Exhaust gas cleaning system using once through sea water under MEPC.340(77).
Operational compliance: Demonstrated compliance with MARPOL Annex VI through onboard records (BDN, MARPOL samples, ECA logs) during PSC inspections.

P

Panama bunker hub: The Pacific and Atlantic terminals of the Panama Canal Authority serve as a Latin American bunker hub.
Particulate matter (PM): Solids emitted in exhaust, influenced by fuel ash and residue.
Peninsula Petroleum: London headquartered bunker supplier with physical operations at Gibraltar, Algeciras, Ceuta, Las Palmas, Panama, and Fujairah.
PFOA-free: A specification for some fuel additives ensuring no per- and polyfluoroalkyl substances are present.
PMS (Power Management System): Not strictly a fuel term but linked to fuel selection during peak loading and cold ironing.
Pour Point: Lowest temperature at which oil flows; key to heating decisions.
Pre-combustion chamber: Engine feature improving ignition of low-cetane fuel, common in some medium speed designs.
PTS (port-to-ship) bunkering: LNG bunkering by pipeline directly from a shoreside terminal to the ship.

Q

Q88: The standard vessel particulars questionnaire format used industry-wide for tanker chartering and vetting.
Quantity dispute: A bunker dispute focused on delivered mass rather than quality, generally addressed via Coriolis records and bunker quantity surveys.
Quay-side bunkering: Delivery of bunkers from a pipeline manifold at a berth, common for distillate at small ports.

R

Raptive: Used in maritime publishing rather than fuel; included only to avoid confusion with maritime acronyms (excluded from this glossary).
Refinery blendstock: An intermediate refinery stream (slurry oil, VGO, cycle oil) combined to make VLSFO or HSFO.
Residual fuel: Heavy residual marine fuel grades RMG/RMK.
RM (Residual Marine): The ISO 8217 designation prefix for residual marine fuel grades (for example RMG 380).
RMA 10 (ISO 8217): A low-viscosity residual grade with a maximum viscosity of 10.00 mm2/s at 50 degrees C.
RMB 30 (ISO 8217): A residual grade with a maximum viscosity of 30.00 mm2/s at 50 degrees C.
RMD 80 (ISO 8217): A residual grade with a maximum viscosity of 80.00 mm2/s at 50 degrees C.
RME 180 (ISO 8217): A residual grade with a maximum viscosity of 180.0 mm2/s at 50 degrees C, with tighter cat-fine limits than RMG 180.
RMG 180 (ISO 8217): The most widely traded residual grade with a maximum viscosity of 180.0 mm2/s at 50 degrees C.
RMG 380 (ISO 8217): A residual grade with a maximum viscosity of 380.0 mm2/s at 50 degrees C and historically the dominant bunker grade for slow-speed engines.
RMG 500 (ISO 8217): A residual grade with a maximum viscosity of 500.0 mm2/s at 50 degrees C.
RMK 380 (ISO 8217): A heavy residual grade with a maximum density of 1.010 kg/m3 at 15 degrees C and maximum viscosity of 380.0 mm2/s at 50 degrees C.
RMK 500 (ISO 8217): A heavy residual grade with maximum density of 1.010 kg/m3 and maximum viscosity of 500.0 mm2/s at 50 degrees C.
RMK 700 (ISO 8217): The heaviest standard residual grade with maximum viscosity of 700.0 mm2/s at 50 degrees C.
ROB (Remaining On Board): Quantity of fuel in tanks at the moment of survey.
Rotterdam: Major Dutch port historically central to European trade.

S

SCR (Selective Catalytic Reduction): NOx abatement using ammonia or urea; integral to many ammonia and dual-fuel installations.
Scrubber (EGCS): An exhaust gas cleaning system that removes SOx (and some PM) from exhaust, allowing continued HSFO use as an equivalent means of compliance.
Sealed Sample: Sample bottle secured with a tamper-evident seal at the time of drawing, retained as evidence in disputes.
Sediment (Total Sediment Existent, TSE): The sediment in a fuel as supplied, measured per ISO 10307-1; ISO 8217 limit for residuals is typically 0.10% m/m.
Sediment (Total Sediment Potential, TSP): The maximum sediment after thermal aging per ISO 10307-2; the operational compatibility test that VLSFO blends are often judged on.
SGS Marine Fuel Services: SGS's marine fuel testing arm offering ISO 8217 analysis, bunker quantity surveys, and condition monitoring.
Shell Marine: Marine fuels and lubricants business of Shell that markets the Alexia, Argina, and Gadinia ranges.
Singapore (port): The world's largest bunker port, delivering over 50 million tonnes of marine fuel per year.
Skangas / Gasum: A Nordic LNG and bio-LNG supplier serving marine bunkering in the Baltic and North Sea.
Slow Steaming: Operating below design speed to save fuel and reduce emissions.
Slurry oil: A heavy aromatic refinery stream used as a VLSFO blendstock; high cat-fine risk.
SOLAS II-2/4: Probability of ignition arrangements covering fuel piping above 220 deg C.
Sox (sulfur oxides): Combustion products of fuel sulfur, regulated by the global 0.50% sulfur cap and 0.10% ECA cap.
Stability: Ability of a residual fuel to remain homogeneous without asphaltene precipitation.
STS (ship-to-ship) bunkering: The transfer of fuel (oil or LNG) from a bunker vessel to a receiving ship moored alongside.
Sulfur cap (ECA 0.10%): The Annex VI Reg 14 limit in force in designated SOx ECAs (Baltic 2010-revised 2015, North Sea 2010-revised 2015, North America 2015, US Caribbean 2015, Med 2025).
Sulfur cap (global 0.50%): The MARPOL Annex VI Reg 14 limit in force since 1 January 2020 on sulfur in fuel oil used onboard ships outside ECAs.

T

Tall oil pitch: A bio-based residual byproduct of kraft pulping, evaluated as a marine biofuel blendstock.
Tank-to-Wake (TtW): Emissions accounting from fuel tank through combustion.
TBN (Total Base Number): Alkalinity rating of cylinder lube oil.
Time-charter bunkers on redelivery (BOR): The fuel onboard at the end of a time charter, valued and reimbursed per the charterparty.
Total (TotalEnergies Marine Fuels): TotalEnergies' marine fuels business and operator of major LNG bunker vessels including Gas Agility and Gas Vitality.
Trafigura: Commodities trader that has invested in CO2 shipping and offshore renewable projects.
TT (truck-to-ship) bunkering: LNG or methanol delivery from a road tanker to the ship at berth.
TTS (terminal-to-ship) bunkering: A pipeline transfer from an LNG/methanol terminal directly to the ship via a quay manifold (sometimes used interchangeably with PTS).

U

Ulsan: South Korean city hosting HHI and Hyundai Mipo Dockyard.
ULSFO (Ultra Low Sulfur Fuel Oil): 0.10% sulfur compliant residual fuel; similar GHG intensity to HFO.
Unitor: A brand of marine chemicals (Wilhelmsen) including bunker additives and fuel treatments.
US Caribbean ECA: SOx and NOx Emission Control Area covering waters around Puerto Rico and the US Virgin Islands.

V

VBPN (Virtual Bunker Pumping Notice): Increasingly used digital bunker delivery documentation, recognized in Singapore's e-BDN initiative from 2023.
VeriFuel: See Bureau Veritas VeriFuel.
Viscosity at 40 degrees C: The reporting temperature for distillate marine fuel kinematic viscosity in ISO 8217.
Viscosity at 50 degrees C: The reporting temperature for residual marine fuel kinematic viscosity in ISO 8217.
Vitol: International commodity trader and Sea Cargo Charter signatory.
VLCC (Very Large Crude Carrier): Tanker between 200,000 and 320,000 DWT.
VLSFO (Very Low Sulfur Fuel Oil): 0.50% sulfur compliant residual fuel; FuelEU's 91.16 g CO2eq/MJ reference value is broadly based on its energy and CO2 characteristics.
Volatile organic compounds (VOC): Hydrocarbon vapors released during cargo and bunker handling, regulated under MARPOL Annex VI Regulation 15 for some tankers.
VPS (Veritas Petroleum Services): International bunker fuel testing and advisory company.

W

Wash water (scrubber): The seawater or fresh water circuit through which exhaust gas SOx is absorbed in an EGCS, regulated under MEPC.340(77) guidelines.
Water content: Free and emulsified water in fuel, limited to 0.50% V/V in most residual grades.
Wedge formula: Calculation correcting bunker quantities for trim and list.
Well-to-Tank (WtT): Emissions associated with fuel production and delivery to the ship.
Well-to-Wake (WtW): GHG accounting basis for GFI under MARPOL Annex VI Chapter 5.