Our knowledgeable experts have built this glossary to help you understand the terminology surrounding fuels and oils. Whether you’re an industry professional or new to the world of fuels and lubricants, this glossary will help you make informed decisions for your fuel systems. You can jump to each section using the links below.
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AdBlue®
A trademarked name for diesel exhaust fluid (DEF). It’s a non-toxic and non-flammable fluid that’s sprayed on to diesel fumes before they leave a vehicle’s exhaust. Its purpose is to reduce harmful pollution by converting nitrogen oxide into nitrogen and water vapour.
Additive
A substance or chemical compound added to a fuel that enhances its performance or lifespan for a given condition.
Alkanes
Compounds that contain carbon and hydrogen atoms that are linked by a single bond. They are the building blocks of many fuels derived from crude oil.
Alternative fuel
Any fuel that can be used in place of conventional fossil fuels and typically offers reduced GHG emissions. These fuels are often renewable, cleaner-burning or derived from non-petroleum sources. Examples include HVO, and GTL.
Anti-wax fuel additive
A type of fuel additive designed to improve the flow of diesel in cold temperatures by lowering the temperature at which waxing can occur.
Aromatic content
The quantity of aromatic compounds in a substance. In fuels and oils, the aromatic content is an indicator of the quality of the fuel as those with higher aromatic content tend to have lower cetane numbers (meaning a lower ignition quality).
Aviation fuel
Fuel designed to power aircraft. There are two main types of aviation fuel: ‘jet fuel’, which is used in turbine engines, and ‘aviation gasoline (avgas)’, which is used in piston engines.
Biodiesel
Also referred to as ‘FAME diesel’ or ‘FAME’, biodiesel is a biodegradable and renewable biofuel made from animal fats, plant oils or recycled cooking oils. Biodiesel can be blended with diesel in various quantities to reduce harmful emissions. It’s produced through a chemical process called transesterification which involves reacting methanol with fats or oils from plants or animals.
Common blends of biodiesel include:
B7 diesel
The most common form of biodiesel which powers engines in diesel vehicles and can be found at all UK forecourts. It’s a blend of 7% biodiesel and 93% diesel.
B100
100% biodiesel that significantly reduces diesel emissions but may require modifications to fuel systems before it can be used.
B20
20% biodiesel blend with 80% diesel commonly used by industrial businesses that want to reduce harmful emissions without switching to 100% biodiesel.
Biofuel
Any fuel produced from renewable or recycled sources instead of fossil fuels. Biofuels can be made from a range of materials such as vegetable oils, animal fats, used cooking waste, hydrogen and many more.
Boiler fuel
A fuel used within a boiler to generate heat. Common boiler fuels used by domestic and off-grid homes include gas and kerosene, whilst many businesses use fuels such as industrial heating oil (IHO) or red diesel for large commercial boilers.
British Standard (BS) 2869
BS 2869 is the standard outlined by the British Standards Institution (BSI) which specifies the requirements for fuels and oils used in agricultural, domestic and industrial applications. Fuels that come under this specification include:
Class A2: an obsolete fuel specification which has been replaced by EN 590. It’s gas oil with a maximum sulphur content of 10ppm (parts per million)
Class C1: the specification for premium home heating oils
Class C2: the specification for regular home heating oils
Class D: the specification for fuels used in in static generators. These fuels contain maximum sulphur content of 1000ppm and are generally used within older fuel systems
British Standards Institution (BSI)
The national standards body of the UK that also collaborates with global institutions such as the International Organisation for Standardisation (ISO). BSI is a non-profit organisation that outlines frameworks and guidelines for a range of industries, products and services.
Bunker fuels
Bunker fuels is the term used to refer to a group of fuels that power or propel a ship. A list of bunker fuels include:
- HFO – Heavy Fuel Oil
- IFO – Intermediate Fuel Oil
- MDO – Marine Diesel Oil
- MFO – Marine Fuel Oil
- MGO – Marine Gas Oil
- ULSFO – Ultra Low Sulphur Fuel Oil
Choosing the right bunker fuel for your ship will depend on a variety of factors such as your vessel or where it operates.
Carbon intensity
The amount of CO2 generated when fuel is used. A lower carbon intensity value indicates a cleaner fuel.
Carbon offset fuels
Counteracting the emissions released from a fuel over its lifecycle. There’s no change to the fuel you use, instead, carbon credits are purchased on your behalf that support carbon-reducing projects around the world. Carbon credits should be independently verified and sourced from certified platforms to ensure sustainability claims are true.
Carbon reporting
Carbon reporting, also referred to as carbon accounting, is the process of measuring and managing greenhouse gas emissions (GHG). It involves an organisation calculating and categorising its carbon emissions before disclosing it to the government and public.
Cetane number
The ignition quality of a fuel. A fuel with a high cetane number ignites faster, meaning a more efficient combustion and improved engine performance.
Class A2 gas oil
Class A2 gas oil is a high-quality gas oil with a maximum sulphur content of 10ppm. It has been discontinued under the BS 2869 specifications and has been replaced by EN 590 gas oil, also known as ultra-low sulphur gas oil or ultra-low sulphur red diesel.
Class D gas oil
A grade of gas oil with high sulphur content (1000ppm) that comes under the Class D BS 2869 specification. It’s a fuel that is predominantly used in static generators and older fuel systems.
Cold filter plugging point (CFPP)
The temperature at which a fuel begins to wax and clog fuel filters. A lower CFPP indicates that a fuel will flow and perform better in colder temperatures.
Compressed natural gas (CNG)
Compressed natural gas is an alternative fuel made by compressing natural gas under high pressure into a significantly smaller volume. It can be used in both automotive and industrial applications to lower emissions when compared to petrol and diesel.
Contaminants
Any unwanted substance that affects the performance of your fuel or system including water, debris, microbes and more. Contaminants can make your fuel unusable and even damage your equipment if left untreated. Fuels that contain FAME such as diesel or biodiesel are more susceptible to contamination due to FAME attracting moisture, meaning that there is a greater need for regular maintenance than with fuels which do not contain FAME.
Crude oil
Crude oil is an unrefined fossil fuel found beneath the Earth’s surface and formed from the remains of animals and plants. It’s a liquid mixture of hydrocarbons extracted by drilling into the ground.
Crude oil fractional distillation
The process of separating the crude oil mixture based on boiling points so that different components can be used to produce various fuels such as petrol, diesel or kerosene.
Density
A fuel’s density measures the mass of a fuel within a specified volume. Fuels with a higher density are typically more efficient because they contain more energy.
Diesel
Diesel is one of the most frequently used fuels in the UK. It can be found at all UK forecourts to power passenger cars and is used by businesses in a range of applications such as automotive, industrial and heating. Diesel is known by many different names, including:
- DERV
- Forecourt diesel
- Fossil diesel
- Petrodiesel
- Road diesel
- Standard diesel
- Ultra-Low Sulphur Diesel (ULSD)
- White diesel
Diesel bug
A common form of microbial contamination within diesel fuel that affects fuel performance and damages fuel systems. It’s caused by bacteria fungi or yeast mixing with water within a fuel tank.
Diesel grades
Summer and winter grades of diesel are supplied depending on the season to improve cold weather performance. Summer grade diesel is typically sold from the middle of March until the middle of November whilst winter diesel is sold throughout the winter months.
- Summer grade diesel – has a higher viscosity making it suitable for warmer temperatures
- Winter grade diesel – contains additives to prevent waxing and improve flow in colder temperatures
Diesel Secure (anti-theft dye)
A fuel additive which dyes diesel fuel blue to deter thieves from stealing it. By turning the fuel blue Diesel Secure makes your fuel easier to trace and thieves are more likely to get caught.
Drop-in fuel
A fuel that can be used within an existing fuel system without needing to make modifications or upgrades.
Emissions
Emissions are gases released into the atmosphere from burning fuel. These gases include carbon dioxide, nitrogen oxide, methane, sulphur dioxide and more.
Energy density
The amount of energy stored within a given volume of fuel. The greater the energy density, the greater the efficiency of the fuel.
EN (European Standards)
EN stands for European Norm and refers to the standards set by the European Standardisation Organisation. While a European set of standards, EN is widely used across the globe to help centralise manufacturing processes.
EN 15940
The European specification for paraffinic diesels. Examples of EN 15940 fuels include HVO and GTL which are more environmentally friendly than traditional diesel.
EN 14214
The European specification and test requirements for FAME biodiesel.
EN 590
The European standard for diesel fuel. EN 590 details the physical and chemical properties that diesel must possess to be used in road vehicles and industrial machinery.
EN 590 diesel
The most common form of diesel supplied in the UK. It’s the diesel that you find at UK forecourts. EN 590 is also used by businesses in vehicle fleets as well as industrial and heating applications.
EN 590 gas oil
EN590 gas oil, also known as EN 590 red diesel, is identical to diesel in terms of its physical and chemical properties but it’s a rebated fuel that is dyed red to differentiate it from non-rebated diesel.
Engine oils
Engine oils are lubricating oils applied between moving engine parts to reduce friction, wear and heat. This is crucial to the performance of the engine and the efficiency of its fuel consumption.
EURO 6
EURO 6 a European emissions standard that sets strict limits on the amount of harmful exhaust emissions that vehicles can product. It applies to all new cars and vans sold in the EU and UK from September 2015 onward.
EURO 7
EURO 7 is the upcoming emission standard for new vehicles in the UK and European Union set to replace EURO 6. It aims to further reduce air pollution from vehicles by tightening limits on harmful emissions and regulating new types of pollution. It focusses on tailpipe emissions and takes into account other aspects of the vehicle such as the tyres, brakes and electric batteries. While EURO 7 has not come into law yet, manufacturers have already started making vehicles with this standard in mind.
FAME
FAME (fatty acid methyl ester) is created through a process called transesterification, where vegetable oils or animal fats react with methanol to form esters (FAME) and glycerol. It can be blended with regular diesel in various quantities and it significantly reduces GHG emissions.
Flash point
The flash point of a fuel is the lowest temperature at which a fuel produces enough vapour to ignite. A low flash point means that a fuel is highly flammable while a high flash point means that a fuel is safer but needs to be at a higher temperature to ignite within an engine.
Fossil fuels
Non-renewable fuels formed from the remains of plants and animals. Examples of fossil fuels include crude oil, coal and natural gas.
Fuel additives
Fuel additives alter the physical and chemical properties of a fuel to improve performance and efficiency.
Fuel duty
A government tax levied on fuel used by vehicles or machinery. In the UK (and many other countries), it’s a fixed amount charged per litre of fuel sold and it contributes significantly to national tax revenue.
Fuel polishing
The process of removing contaminants from a fuel by pushing it through an advanced filtering system.
Fuel system inspection (FSI)
A suite of 60 checks to ensure that a site’s fuel infrastructure is running at maximum performance. An FSI identifies problems and makes actionable recommendations so that organisations can act to avoid unplanned downtime.
Fuel testing
A service that involves taking samples from the top, middle and bottom of a fuel tank and testing it at a laboratory to identify any contaminants or defects.
Fuel uplift
The process of safely removing or transferring fuel from a fuel tank into another tank or vehicle. It requires expert handling to avoid the fuel spilling into the nearby environment.
Gas oil (red diesel)
Gas oil is a rebated form of diesel that is marked red to differentiate it from regular diesel. It can only be used by certain sectors in off-road vehicles and machinery.
Generator fuel
Also known as backup fuel, generator fuel gets its name because it is fuel used in backup generators. Generator fuel is no specific fuel and does not need to be used in generators, it can refer to a number of fuels including diesel, red diesel and HVO fuel.
Green diesel
A name used interchangeably with HVO fuel, a 100% renewable diesel that reduces net emissions released from fuel consumption by up to 90%.
Greenhouse gases (GHGs)
Warming gases that trap heat in the Earth’s atmosphere, contributing to global warming as a result of the greenhouse effect.
GTL fuel (gas-to-liquid)
GTL fuel is a cleaner burning diesel alternative derived from natural gas. It is more environmentally friendly than diesel and comes under EN 15940 specifications for paraffin diesel.
H2 (hydrogen fuel)
H2 fuel refers to hydrogen gas that is used as a source of energy. It’s a clean burning fuel that only produces water and can be burned in specifically-designed engines, turbines or in fuel cells to generate electricity through an electrochemical reaction.
Heating oil
A collective term for liquid fuels used to heat homes, farms and buildings. These fuels include kerosene, diesel, industrial heating oil and more.
Hydraulic oil
Hydraulic oil, also referred to as hydraulic fluid, is used to transfer power and lubricate components within a hydraulic system. It’s a non-compressible fluid that helps to control movement while protecting parts, removing contaminants and dissipating heat. Hydraulic oil comes in a variety of forms with varying properties that make it suited to a range of applications. Types of hydraulic oil include:
- H and HH – which contain no additives
- HL – contains additives that prevents rust and oxidation
- HLP – a more advanced version of HL that also increases load-bearing capacity
- HLPD – similar to HLP but contains additives that enhances particle removal and dispersion capacity
- HM – hydraulic oil used in mobile hydraulic systems such as excavators and cranes
- HV and HVLP – high viscosity hydraulic fluids that are suitable for a wide range of temperatures
Hydrotreated vegetable oil (HVO fuel)
A second-generation, fully renewable biofuel and diesel alternative that reduces net CO₂ emissions by up to 90%. Produced by hydrotreating vegetable oils from 100% renewable sources, HVO is free from FAME, fully compatible with diesel, and requires no engine or fuel system modifications. Classified as a paraffinic diesel, it meets EN 15940, ASTM D975, and Fuel Quality Directive 2009/30/EC Annex II standards.
HVO is also referred to as:
- Renewable diesel
- HVO100
- Green diesel
- Red HVO
- White HVO
Industrial heating oil (IHO)
IHO is a drop-in replacement for diesel, used for commercial heating, boiling and drying applications. It’s a rebated fuel with the same physical properties and calorific value as diesel which makes it a cost-effective fuel for heating applications.
Intermittent use
Fuel systems that are not continuously being used such as backup generators. These systems require more stable fuel that can be stored for longer periods of time and in a wide variety of temperatures, such as HVO.
ISCC (International Sustainability & Carbon Certification)
The ISCC is an independent certification scheme which ensures sustainability and traceability across supply chains.
ISO (International Organisation for Standardisation)
The ISO is an independent organisation that publishes specifications, frameworks and requirements for businesses and organisations across the globe. Working across all sectors, the ISO aims to help organisations by standardising processes to create universal understanding.
ISO 14064
An internationally recognised framework for monitoring, managing and reporting GHG emissions. It is part of the wider ISO 14000 set of standards for environmental management. ISO 14064 is broken down into 3 aspects which are:
ISO 14064-1
This framework outlines the requirements for quantifying, managing and reporting GHG emissions at an organisational level.
ISO 14064-2
This framework outlines the requirements for quantifying, managing and reporting GHG emissions at a project level.
ISO 14064-3
ISO 14064-3 details the needs for verifying and validating the accuracy of GHG emissions.
ISO 14068
The ISO 14068 framework outlines the requirements needed for organisations to achieve carbon neutrality. It adopts a hierarchical approach which requires organisations to demonstrate a reduction in carbon emissions before considering offsets.
ISO 22241
The international specification for AdBlue®. It defines the chemical and physical requirements of AdBlue® to ensure quality, and outlines how to store and handle the diesel exhaust fluid.
ISO 8217
ISO 8217 is a framework which specifies the requirements for fuels and oils used in marine diesel engines and boilers. The specification covers various oils including both distillate and residual marine fuels whilst outlining test methods that should be used to ensure a fuel meets the requirements.
ISO VG
An international system used to classify viscosity grades of industrial oils including lubricants, greases, hydraulic oils and more.
Jet A1 (jet fuel)
Jet fuel is highly refined kerosene used in aircraft which has a high flash point and a much lower freezing point, due to the exposure of extreme conditions at high altitudes.
Kerosene
Kerosene is a refined fuel which is predominantly used for home heating and lighting. It has many other names in the UK including:
- Home heating oil
- Paraffin
- 28-second oil
- Burning oil
- Lamp oil
- Kero
Kerosene lubricity additive
A kerosene lubricity additive is a chemical compound added to kerosene or kerosene-based fuels to reduce wear within fuel systems and generators.
Kinematic viscosity
A measure of a fuel or oil’s resistance to flow under the force of gravity. This is particularly important for fuel systems where gravity is the dominant force such as through pipework. It describes how easily a liquid flows and is especially important in fuel and lubricant performance.
Kleenburn kerosene
Kleenburn kerosene is also referred to as ‘premium kerosene’ or ‘carbon clean kerosene.’ It’s a blend of kerosene fuel and several precision additives that provide performance and environmental benefits.
Liquefied natural gas (LNG)
Natural gas that is cooled into a liquid state under extreme conditions. LNG is typically used to transport natural gas and is formed when natural gas reaches -162°C. The liquid is often converted back to gas to be used as a fuel.
Liquefied petroleum gas (LPG)
Derived from natural gas, LPG is a highly flammable fluid consisting of propane and butane which is stored under high pressure and is mostly used in central heating systems and cooking equipment (such as a barbeque).
Lubricant
An oil or grease used to protect moving parts in engines, industrial machinery and other various applications. Lubricants reduce wear, friction and heat to improve efficiency and lifespan of parts.
Lubricity
Lubricity is a measurement of an oil’s lubricating properties, determining the amount of wear and corrosion it has prevented. It’s calculated by measuring the wear scar diameter (WSD) in micrometers (μm) against a test ball under controlled conditions.
Marine gas oil
A distillate fuel used to propel and heat marine vessels. It’s a form of bunker fuel with low sulphur content which ensures it’s compliant with sulphur emissions standards outlined by the International Maritime Organisation (IMO). Marine gas oil is a type of diesel fuel with a high energy density, making it suitable for long voyages.
Microbial contamination
Microbial contamination refers to the presence and growth of microorganisms, such as bacteria, fungi, and yeasts in fuel systems, especially where water and fuel coexist.
Net zero
The balance between emissions released into the atmosphere and emissions removed from the atmosphere. Achieving net zero means a company, country, or individual is no longer adding to the total amount of GHGs in the atmosphere. The UK has signed into law a target to reach net zero emissions by 2050 in line with the Paris agreement.
Off-road fuel use
Fuel which is used in off-road machinery and vehicles, such as red diesel.
OFTEC
A trade organisation which oversees the heating and cooking industries within the UK and Ireland. OFTEC works with the government national standards agencies and certification bodies to provide guidance and training to ensure technicians are accredited and work in compliance with all relevant regulations.
Oil tank monitoring
The process of viewing oils or fuel levels remotely using an advanced tank telemetry system. It uses cellular technology to upload fuel data to satellites which allows users to view fuel levels in an online dashboard.
Oxidation stability
The measurement of a fuel’s oxidation when it’s exposed to oxygen. When a fuel is oxidised, it can damage combustion engines which is why it’s crucial that a fuel is stable.
Paraffin
Paraffin is a term used interchangeably with kerosene – it is a highly flammable hydrocarbon liquid used for heating and lighting in the UK, especially in off-grid homes.
Paraffinic diesel
A family of synthetic diesel which is also referred to as ‘clean diesel.’ These fuels contain zero sulphur and aromatic content, which enables them to significantly reduce emissions. Examples include GTL and HVO.
Particulate matter
Liquid or solid particles that are a byproduct of incomplete fuel combustion. They are a form of emissions consisting of chemical compounds including carbon, nitrates and sulphates.
PAS 2060
A standard for demonstrating carbon neutrality developed and published by the British Standards Institution (BSI). PAS 2060 has now been replaced by ISO 14068.
Petrol
A fuel used in spark-ignition vehicles and engines.
Priority fuel contracts
Also known as emergency fuel contracts, a priority fuel contract enables you to jump the queue and guarantees your fuel supply within a pre-agreed timeframe in the event of an emergency.
RDCO (Registered Dealer in Controlled Oils)
RDCO is a government scheme that requires all distributors of controlled oils to be registered with them. Users of controlled oils must also declare they are eligible using an RDCO form.
Red diesel (gas oil)
Red diesel (gas oil) is marked diesel which has been dyed red to differentiate it from road diesel for tax purposes. Both red and white diesel have the exact same physical and chemical properties; however, red diesel is a rebated fuel whilst diesel is subject to the full rate of fuel duty. Red diesel also goes by other names, including:
- Gas oil
- Rebated diesel
- Tractor diesel
- Cherry red
- 35-second diesel
Red diesel can only be used off-road and by sectors which are eligible to use rebated fuels.
Renewable Fuels Assurance Scheme (RFAS)
A scheme manged by Zemo which aims to verify the sustainability claims made by suppliers of renewable fuels. RFAS is an independent initiative which runs alongside the RTFO outlined by the UK government.
Renewable Transport Fuel Obligation (RTFO)
The RTFO is a UK government scheme that mandates fuel suppliers who sell over 450,000 litres of fuel to increase the number of sustainable fuels they supply each year.
Scope 1, 2 & 3 emissions
Scopes used to categorise carbon emissions for the purpose of carbon reporting.
Scope 1: the emissions generated as a result of direct activities of the organisation. An example of scope 1 includes the emissions released from fuel consumption.
Scope 2: the emissions generated from the consumption of energy such as electricity.
Scope 3: the indirect emissions generated from the companies supply chain and products. These include both upstream and downstream emissions over a product’s lifecycle.
Selective catalytic reduction (SCR)
A technology used to reduce nitrogen oxide emissions after combustion and before it leaves the exhaust. AdBlue® is a fluid which is commonly used in SCR systems.
Sludge
Solid and semi-solid buildup at the bottom of your fuel tank as a result of fuel degradation and contamination. Sludge clogs filters, reduces performance and damages fuel tanks and systems.
Storage stability
A fuel’s or lubricant’s ability to maintain its quality, performance, and chemical properties over time while in storage. It determines how well a fuel can resist oxidation, polymerisation, microbial growth and more.
Sulphur content
The amount of sulphur present in fuel. Fuels with a low sulphur content produce fewer sulphur dioxide emissions and reduce wear and corrosion in engines and fuel systems, increasing lifespan and performance.
Sustainable Aviation Fuel (SAF)
SAF is a jet fuel produced from renewable feedstocks such as waste oils, animal fats, plants and more. It is estimated to reduce net GHG emissions by up to 80% and thus has been adopted by many aviation businesses to as a cleaner alternative to jet A1 fuel.
Tank cleaning
The process of cleaning a fuel tank either externally or internally via man entry. A tank clean removes harmful sludge, debris and sediment from the tank to improve fuel efficiency and protect tanks and fuel systems from degradation.
Tank decommissioning
Safely putting a fuel tank out of service permanently or temporarily via foam filling. To decommission a tank, it must be completely filled with concrete or foam to prevent buildup of flammable vapours and ensure stability.
Tank lining
Tank lining, also known as a double wall system, involves adding an additional layer of protection inside a fuel tank to stop fuel leaks, extend tank life and prevent environmental damage.
Tank telemetry monitoring system
A monitoring system which enables you to view fuel levels remotely by installing an advanced sensor to your tank. Using cellular technology, a telemetry monitoring system uploads fuel data for users to view in an app or online dashboard.
Transesterification
The process of combining alcohol with triglycerides to produce biodiesel (FAME), a renewable fuel which provides significant environmental benefits over diesel. Triglycerides are the main components of animal and vegetable oils which convert into FAME when they react with alcohol.
Viscosity
Viscosity is the measurement of a fuel or oil’s flow. High viscosity oils are thicker and flow slowly through a fuel system whilst low viscosity oils flow quickly through fuel systems. The viscosity you require will be determined by your individual equipment and may also be influenced by external factors such as the weather.
Viscosity index
Viscosity index determines the stability of an oil’s viscosity at different temperatures. A high viscosity index means that oil is more stable whilst a low viscosity index means that an oil is less stable.
Waste oil collection
The process of safely removing redundant fuels or oils from a site. If suitable, collected oils can be recycled or put back into use.
Waxing
Waxing is the process of paraffin wax solidifying at low temperatures. While paraffin wax provides lubricating benefits within diesel fuel, when solidified it can clog fuel filters and damage fuel systems.
Zemo Partnership
Zemo partnership are a non-profit organisation which aim to help shape government transport policy to reduce emissions, improve air quality and combat climate change.
Zero emissions vehicle
A vehicle that generates no tailpipe emissions such as an electric vehicle.