Glossary

A lubricant additive that keeps soot, oxidation products and other finely divided insoluble material suspended, reducing agglomeration and deposit formation. A dispersant does not remove the contamination, so oil condition, filtration and change intervals remain important.

An additive that modifies the formation and growth of wax crystals so that a wax-containing oil or fuel remains mobile at a lower temperature. It does not remove wax and may not produce an equivalent improvement in every cold-flow property or operating system.

An additive that reduces chemical or electrochemical attack on metal surfaces, commonly by forming a protective film, displacing water or neutralising corrosive species. The protected metals and operating conditions should be specified because one inhibitor may not protect every material.

Zinc dialkyldithiophosphate, a family of multifunctional lubricant additives used principally for anti-wear and antioxidant protection. ZDDP forms protective surface films under boundary lubrication and contributes zinc, phosphorus and sulphur to the formulation, which can affect emissions-control systems and lubricant ash limits.

An oil-soluble polymer that reduces the rate at which a lubricant loses viscosity as temperature rises, enabling formulations such as multigrade oils. It raises the finished lubricant's calculated viscosity index, but mechanical or thermal degradation of the polymer can reduce its thickening effect in service.

The progressive smoothing of a cylinder liner's running surface until it develops a polished or mirror-like appearance. Hard piston deposits or abnormal contact can remove the surface texture and oil-retaining features, weakening the lubricant film and increasing the risk of wear, blow-by and scuffing.

The controlled delivery of fuel through one or more injectors into an engine's intake air or directly into its combustion chamber. Injection pressure, quantity, timing and spray pattern influence mixture formation, combustion efficiency, emissions and component temperatures, and must suit the engine and fuel.

An engine-combustion system in which an electrical spark initiates burning of a prepared fuel-air mixture. It is commonly used with petrol and gaseous fuels and differs from compression ignition, where fuel ignites in hot compressed air without a spark plug.

A hard, smooth and often glossy deposit formed when lubricant and combustion-derived degradation products bake onto hot engine surfaces, particularly pistons, ring zones and cylinder liners. Lacquer can restrict moving parts and impair lubrication or heat transfer; the term overlaps with varnish, so inspection reports should describe the deposit's location and physical character.

Lubricant degradation caused by reaction with nitrogen-oxide combustion products, particularly in spark-ignition and gas engines. Nitration products can increase oil acidity, viscosity, insolubles and deposit formation and are commonly monitored by trending Fourier-transform infrared spectroscopy results alongside other oil-condition tests.

A broad consumption tax used in many jurisdictions and operating on value-added principles similar to VAT. Businesses generally charge GST on taxable sales and claim credits for eligible tax paid on inputs, while rates, registration, exemptions and marine-supply treatment are determined by local law.

Gas oil containing prescribed chemical markers and, in some jurisdictions, coloured dye to identify a reduced-duty or otherwise controlled fiscal status. Marking does not define the fuel's technical quality or marine suitability, and the permitted uses vary by law; in marine trading, the term should be written out because "MGO" more commonly means marine gas oil.

A broad consumption tax charged on the value added at successive stages of supplying goods and services, with qualifying businesses generally deducting input tax from output tax. The final burden is intended to fall on consumption, but the rate, place of supply, zero-rating, exemption and recovery rules for yacht fuel and lubricants vary by jurisdiction and vessel use.

Fuel taxed at a reduced rate of excise duty because it is intended for a legally permitted use. It is not the same as duty-free fuel: part of the normal duty may still be payable, and eligibility, marking, documentation and restrictions on subsequent use are determined by the relevant jurisdiction.

Fuel supplied without payment of a duty under a specific exemption, relief or duty-suspension arrangement, commonly subject to an eligible vessel, voyage or use and prescribed records. "Duty-free" does not automatically mean free of VAT, GST or all taxes, and diversion to an ineligible use can trigger assessment, penalties and recovery of duty.

An empirical index calculated from the density and viscosity of a residual fuel to provide a readily available indication of possible ignition performance. A higher CCAI is generally associated with a greater risk of prolonged ignition delay, but the value is not a direct measurement of aromatic content, ignition delay or combustion quality and should not be used alone as a pass-or-fail assessment.

The heat released by complete combustion of a specified quantity of fuel when the water formed remains as vapour and its latent heat is not recovered. It is also called lower heating value or net calorific value and is normally the more relevant basis for comparing energy available to a non-condensing engine.

A laboratory apparatus used to assess diesel-fuel lubricity by moving a loaded steel ball repeatedly across a stationary steel disc immersed in the test fuel under controlled conditions. The result is reported as a wear-scar diameter, with a smaller corrected wear scar generally indicating better lubricity under the test conditions.

The mass of a substance per unit volume at a stated temperature, commonly reported for liquid fuels in kilograms per cubic metre at 15°C. Density is used in quantity conversion, fuel identification and treatment calculations, and must be temperature-corrected when observed and reference conditions differ.

A measure of a fluid's resistance to shearing flow, defined for a Newtonian fluid as shear stress divided by shear rate. It is normally expressed in pascal-seconds or millipascal-seconds, varies strongly with temperature and is related to kinematic viscosity through the fluid's density.

The capability of an engine or other energy-conversion system to operate on two different fuels. In marine use, this commonly means a gaseous or low-flashpoint fuel used with a small quantity of pilot oil, with operation on oil fuel alone also possible where the system is designed for it.

A fuel intended to replace or supplement a conventional fuel without substantial modification to the existing engine, fuel system or supply infrastructure. Drop-in suitability is specific to the application and does not remove the need to confirm the fuel specification, material compatibility, storage behaviour and engine-maker approval.

A fuel consisting principally of propane, butane or a mixture of the two, stored and handled as a liquid under pressure or refrigeration. Its composition affects properties such as vapour pressure and energy content, and marine use requires fuel systems and safety arrangements designed for the product supplied.

A fuel produced by combining two or more components in controlled proportions to obtain particular properties or meet a specification. The quality and suitability of the finished blend depend on the components, their proportions and their compatibility, not solely on the properties of each component before blending.

Natural gas, composed principally of methane, stored as a gas under high pressure to reduce its volume. CNG requires purpose-designed pressure vessels and fuel equipment, and its comparatively low volumetric energy density can restrict its practicality for marine use.

A standardised hazard-communication document describing a product's classification, composition, safe handling and storage, exposure controls, emergency measures, transport and disposal information. SDS is the current term under the Globally Harmonized System, while MSDS is an older name; neither document certifies product quality or equipment suitability.

A document acknowledging the physical receipt of a bunker delivery and commonly recording the vessel, supplier, products, stated quantities and delivery times. It is not the same as the statutory Bunker Delivery Note, and signature should not be assumed to waive recorded protests or constitute final acceptance of quality or quantity unless the contract says so.

A contemporaneous written record that one party objects to an event or condition during a delivery, such as an apparent shortage, unsafe procedure, sampling refusal, delay or document discrepancy. It should state the facts, time, persons involved and reservation of rights, but it does not by itself prove a claim or replace any contractual notice-of-claim requirements.

A formal communication stating that a party is making, or preserving the right to make, a contractual claim and identifying its nature and basis. It must be sent to the required recipient in the prescribed form and within the applicable time bar, with the information and supporting documents required by the contract.

A preliminary commercial document showing the products, anticipated charges and payment details for a proposed or conditional supply, often used to request advance payment or support customs arrangements. It is not normally the final tax or accounting invoice, which should be issued when required after payment or supply.

A synthetic hydrocarbon base fluid produced by combining alpha-olefin molecules into larger, controlled structures. PAOs are used in lubricants requiring properties such as a high viscosity index, low-temperature fluidity and low volatility, normally together with additives and sometimes other base stocks.

The ability of a lubricant or hydraulic fluid to allow entrained air bubbles to separate after the air source is removed. It is commonly reported as the time required for entrained air to fall to a specified level under stated test conditions and is distinct from the tendency to form surface foam.

A descriptive classification for base oil whose viscosity changes comparatively little as temperature changes. The term does not define a finished-lubricant performance level, and any numerical boundary should be linked to the classification system being used.

An engine or automotive gear lubricant classified in a single SAE viscosity grade rather than in both a winter and a higher-temperature grade. A monograde designation describes viscosity behaviour only and does not establish the oil's performance category or approval status.

A lubricating fluid used as the principal component of a finished lubricant before the required additives are incorporated. Base stocks may be mineral, re-refined, synthetic or derived from other sources, and their properties strongly influence the viscosity, volatility and temperature behaviour of the finished product.

The ability of a grease to retain its consistency and structure when subjected to mechanical working or shear. Poor mechanical stability can cause excessive softening, hardening or oil separation, leading to leakage, restricted flow or inadequate lubrication.

The temperature at which the first drop of material falls from a grease under a specified laboratory test. It indicates a change in the thickener structure at elevated temperature but is not the grease's maximum continuous operating temperature, which is normally lower and depends on the complete formulation and application.

A semi-solid lubricant made by dispersing a thickening agent in a lubricating fluid, normally with additives to provide additional properties. Its consistency allows it to remain in place where a liquid lubricant might drain or leak away.

A grease thickened principally with a lithium soap. Conventional lithium and lithium-complex greases have different high-temperature characteristics, and the description alone does not establish consistency, load-carrying performance or compatibility with another grease.

The minimum shear stress required to make a grease or other plastic material begin to flow continuously. Below this value the material behaves predominantly as a solid; the measured or estimated value depends on temperature, test method and the sample's prior mechanical history.

In marine emissions control, AUS 40 is a high-purity solution containing nominally 40% urea by mass in demineralised water and supplied to a selective catalytic reduction system. The solution releases ammonia in the exhaust stream so the catalyst can reduce nitrogen oxides; it is not a fuel or lubricant and should not be confused with the nominal 32.5% automotive solution AUS 32.

The general propensity of a fuel to obstruct or restrict fuel-system filters during storage or use. It may result from particles, wax crystals, oxidation products, sludge, microbial material or incompatible components and should not be confused with cold filter plugging point, which is a specific low-temperature test.

A dimensionless heavy-fuel stability parameter indicating the available solvency for keeping asphaltenes dispersed relative to their solvency requirement. A higher P-value generally indicates a greater stability reserve, but the test method and interpretation criteria must be stated because P-value is a supplementary, method-dependent assessment rather than an ISO 8217 specification property.

The proportion of fatty acid methyl ester present in a finished fuel, normally determined by a specified analytical method and reported as a volume or mass fraction. The result is used to confirm a blend designation or contractual limit because even relatively low FAME content can affect storage, water handling and material compatibility.

A standard test in which a polished copper strip is exposed to a fuel or other petroleum product under prescribed conditions and the resulting tarnish is compared with a reference scale. It indicates the potential presence of compounds corrosive to copper, particularly reactive sulphur species, but does not predict corrosion of every material in service.

The combined concentration of aluminium and silicon measured in a fuel and normally reported in milligrams per kilogram. In residual marine fuel it is used as an indicator of catalyst-fine contamination, but does not show particle size, hardness or the full quantity of abrasive material reaching the engine.

A contractual deadline by which a claim, notice or supporting documents must be submitted. Failure to comply can extinguish or restrict the claim even if the underlying complaint is valid, so the required recipient, form, content and deadline must be checked in the governing terms rather than assumed from industry practice.

The contractually agreed basis for deciding whether delivered fuel meets the required quality. It normally identifies the specification, representative sample, test methods, laboratory and rules for interpreting results, and provides the evidential basis for acceptance or a quality claim.

A formal assertion that the amount delivered was less than, or otherwise differed from, the contractually determined quantity. It should be notified within the applicable time bar and supported by the agreed measurement records, calibration information, delivery documents, tank or meter data and any contemporaneous letter of protest.

The quantity and grade of fuel ordered or arranged for delivery to a vessel. The term may also be used more generally to refer to the bunker order or delivery as a whole.

The contractually defined point at which responsibility for accidental loss of or damage to the fuel passes from one party to the other. It should be identified separately from title transfer, payment and quantity determination because these events may occur at different times.

A synthetic liquid hydrocarbon fuel produced from natural gas, commonly by converting the gas into synthesis gas and then forming hydrocarbons through the Fischer-Tropsch process. GTL diesel is generally paraffinic and may be used alone or as a blend component where it meets the required fuel specification and engine-maker requirements.

A general commercial term for a marine distillate fuel that is usually heavier than marine gas oil and may contain traces of residual components. The name does not establish a complete specification, so the required ISO grade and other contractual properties should be stated when ordering.

A code identifying a category and grade of marine fuel specified under ISO 8217 and the related ISO 8216 classification system. The designation distinguishes fuel families such as distillate and residual fuels and, where applicable, particular composition or viscosity classes; the relevant standard edition should also be stated.

Fuel carried by a vessel for its own consumption rather than as cargo. The term may refer to the fuel onboard, the quantity supplied or, more generally, a bunker purchase or delivery.

Chemical compounds containing only carbon and hydrogen. They are the principal components of petroleum-derived fuels and lubricants and can also be manufactured from synthetic or renewable feedstocks.

The regulation in MARPOL Annex VI controlling emissions of sulphur oxides and particulate matter, principally through limits on the sulphur content of fuel oil used or carried for use. The current maximum is 0.50% by mass outside designated sulphur Emission Control Areas and 0.10% by mass within them, unless an approved equivalent compliance method such as an exhaust-gas cleaning system is used.

The ability of a substance to be broken down by microorganisms into simpler products under specified conditions. Results depend on the test, environment, duration and endpoint—such as primary, ultimate, ready or inherent biodegradation—so "biodegradable" should not be used without a recognised method and criterion and does not mean non-toxic or harmless if spilled.

The principal IMO treaty setting minimum international standards for the construction, equipment and operation of ships consistent with their safety. SOLAS 1974, as amended, covers matters including machinery, electrical and fire safety, lifesaving appliances, navigation, dangerous goods and safety management; its fuel provisions include flashpoint controls and mandatory requirements for ships using low-flashpoint fuels.

The annex to the International Convention for the Prevention of Pollution from Ships containing regulations for the prevention of air pollution from ships. It controls matters including sulphur oxides, particulate matter, nitrogen oxides, ozone-depleting substances, volatile organic compounds and shipboard incineration, and also contains energy-efficiency and carbon-intensity requirements.

A commonly used name for an Emission Control Area designated under MARPOL Annex VI to control sulphur oxides and particulate matter, where the 0.10%-by-mass fuel-sulphur limit applies unless an approved equivalent method is used. The legal text generally uses "Emission Control Area"; not every ECA has identical pollutant coverage, so a sulphur ECA should not be confused with an area designated only for nitrogen-oxide controls.

A sealed counterpart sample retained by the physical supplier or seller for quality assurance and possible dispute resolution. Its evidential value depends on showing that it came from the agreed sampling operation and remained correctly identified, sealed, stored and traceable.

A sample taken after bunkering from a receiving tank, line or treated fuel system. It shows the condition at that sampling point after transfer and may contain previous tank contents or onboard contamination, so it cannot automatically establish the quality of the fuel as delivered.

A sample whose collection, division, labelling and sealing are observed by representatives of the relevant parties or an agreed independent person. Witnessing strengthens the record of provenance but does not correct an unsuitable sampling point or method, so any objection should be recorded at the time.

The unique identifier marked on a sample seal and recorded on the sample label, custody records and relevant delivery documents. Matching numbers support traceability, but the number alone does not establish that the sample was correctly drawn or that its seal and custody remained intact.

A tamper-evident security device applied to a sample container after filling to discourage or reveal unauthorised opening or substitution. It should carry a unique identifier and be applied, witnessed and recorded in accordance with the relevant regulatory or contractual procedure.

In gears and rolling bearings, a surface-fatigue form of damage in which small pieces of material break away after repeated contact stresses, leaving pits. It should be distinguished from superficially similar pits caused by corrosion, cavitation or electrical damage.

A solid material that reduces friction and wear by forming a low-shear layer between surfaces. Examples include graphite, molybdenum disulphide and polytetrafluoroethylene; solid lubricants may be applied directly or incorporated into grease, paste or coating, and must be compatible with the materials and operating environment.

A lubrication regime in which the fluid film does not fully separate the moving surfaces and a substantial part of the load is carried through surface asperities and protective boundary films. Correct anti-wear or extreme-pressure chemistry and suitable surface condition are particularly important in this regime.

A full-film lubrication regime in which relative motion draws a viscous lubricant into a converging clearance and generates pressure sufficient to support the load and separate the surfaces. Film formation depends principally on speed, viscosity, load and geometry and may be lost during starting, stopping or lubricant starvation.

A severe form of adhesive wear caused by breakdown of the protective lubricant film between sliding surfaces. Local metal-to-metal contact, welding and tearing can produce rough or smeared damage and a rapid rise in friction and temperature; high load, sliding speed, inadequate viscosity or unsuitable additive protection can increase the risk.

The vertical distance from a defined reference point at the top of a tank to the liquid surface. A measured ullage is converted to volume using the tank's calibration table and should be distinguished from sounding, which measures liquid depth from a lower reference point.

The measurement of the depth of liquid in a tank from a defined sounding reference point, traditionally using a calibrated tape or rod and sometimes an electronic gauge. The reading is converted to volume using the correct tank table, with trim, list, temperature and free-water corrections applied where relevant.

The rate at which fuel or another fluid is discharged by the delivery facility, usually expressed as volume or mass per unit of time. The agreed minimum, average or maximum rate should be distinguished, and actual performance may be limited by pump capacity, product viscosity, hose size, back-pressure and safe operating pressure.

The physical coupling point and associated fittings through which fuel is transferred between the delivery system and the receiving vessel. Connection type, flange or coupling standard, diameter, pressure rating, gasket, reducers and bonding or earthing arrangements should be confirmed before delivery.

The maximum safe rate at which the receiving vessel can accept fuel into the nominated tanks and pipework. It may be lower than the supplier's pumping capability and depends on tank capacity, venting, line arrangement, valve operation, monitoring and the vessel's approved procedures.

The formation of a dispersion in which droplets of one liquid are suspended within another liquid with which it does not normally mix. Agitation and surface-active substances can create or stabilise an emulsion, making subsequent separation more difficult.

The ability of a lubricant or other fluid to separate from water after the two have been mixed. Standard tests report the separated oil, water and emulsion layers or the time required for separation at a stated temperature; good water separability supports settling and drainage but does not mean the fluid is unaffected by water.

The process by which an emulsion breaks into separate liquid phases, or the ability of a fluid to promote that separation. In lubricants, good demulsification helps water settle out for removal instead of remaining dispersed through the oil.

Unable to form a single homogeneous liquid phase when mixed in the proportions and under the temperature and pressure conditions concerned. Immiscible liquids normally separate into distinct layers, although agitation can temporarily disperse one as droplets in the other.

The ability of a fuel, lubricant or other fluid to resist reaction with oxygen during storage or service. Oxidation can form acids, gums, varnish, sludge and viscosity-changing products; accelerated laboratory tests are comparative and do not provide a universal prediction of storage or service life.

A fuel containing fatty acid methyl ester blended with a petroleum-derived, synthetic or renewable hydrocarbon fuel. The FAME proportion and applicable finished-fuel specification should be stated because FAME content can affect oxidation stability, cold-flow behaviour, water affinity, material compatibility and storage life.

A fuel produced wholly or partly from biomass, including recently derived biological material and certain biological wastes or residues. The term covers different fuels and production pathways and, by itself, does not establish product quality, sustainable origin or a particular lifecycle greenhouse-gas saving.

A methane-rich gas produced from biomass, commonly by upgrading biogas to remove carbon dioxide, water, hydrogen sulphide and other impurities, or by gasification followed by methanation. When conditioned to the required quality, it can be compressed, liquefied or introduced into a gas network for use in place of fossil natural gas.

Synthetic fuel is fuel manufactured by chemical synthesis from feedstocks such as synthesis gas, hydrogen and a carbon source rather than obtained directly by conventional petroleum refining. An e-fuel is a type of synthetic fuel for which electricity provides the principal production energy, often through electrolytic hydrogen; the terms are therefore related but not interchangeable, and neither term alone proves renewable origin or low lifecycle emissions.

A term for renewable diesel whose principal components are hydrocarbons rather than fatty-acid esters. It may be used neat or blended with conventional diesel where the finished fuel meets the required specification and is approved for the intended engine and fuel system.

A US customary unit of liquid volume equal exactly to 3.785411784 litres. It must be identified as a US gallon because it is smaller than an Imperial gallon; fuel-volume quotations should also state the applicable reference temperature.

A portable, usually cylindrical container with a handle used for lubricants, greases and other fluids. Pail capacity is not a fixed unit—common nominal sizes include approximately 18 or 20 litres—so the product's stated net volume or mass controls.

A rigid, composite or flexible portable package designed for mechanical handling and for quantities between conventional packages and bulk tanks. Liquid lubricants and fluids are often supplied in nominal 1,000-litre IBCs, but capacity, transport approval, construction material, filling limit and product compatibility must be confirmed.

A unit of mass equal exactly to 1,000 kilograms; the standard symbol is t, while MT is widely used commercially. It is not a unit of volume, and conversion between tonnes and litres or gallons requires the product's density at a stated reference temperature.

A metric unit of volume equal exactly to one cubic decimetre or 0.001 cubic metre. Fuel volume changes with temperature, so commercial quantities in litres should state whether they are observed volumes or have been corrected to a reference temperature such as 15°C.