Fuel and Oil Terms Glossary

Fuel and Oil Terms Glossary

The world of fuels and oils is filled with technical jargon, making it hard to know which products or services are right for you. That’s why our experts have compiled a clear, easy-to-understand glossary of the most used terms, so you can make confident, informed decisions for your business or home.

A

AdBlue

A fluid used in diesel engines to reduce harmful NO_x emissions – it’s stored in a separate tank in your vehicle and is mixed in after combustion. Made to strict ISO 22241 standards, only licensed suppliers (approved by the German VDA association) can sell it under the registered AdBlue® name. You might also hear it being called AUS 32 or diesel exhaust fluid (DEF).

Additive

Chemicals mixed in to improve how the fuel performs or how long it lasts – think of them as boosters for your fuel. Common types include anti-wax agents (great in winter), anti-rust protectors, and cleaners.

Alkanes

The basic building blocks of fuels like petrol and diesel. Found in crude oil, they’re hydrocarbons that differ by length – shorter ones boil easier, longer ones don’t.

Alternative fuel

Anything that’s not your standard fossil fuel – like HVO, biodiesel, LNG, or CNG. These are often cleaner and more eco-friendly options.

Anti-wax fuel additive

Fuel tends to “wax up” in cold weather – basically, it thickens and can block filters. Anti-wax additives help to prevent that by changing how the crystals form, which keeps the fuel flowing and your engine running smoothly.

Aromatic

How many “aromatic hydrocarbons” (a specific type of compound) are in your fuel. It affects how cleanly it burns and what kind of emissions it gives off.

Aviation fuel

Specialised petroleum-based or petroleum and synthetic fuel blends made for aircraft. There are two main types: Jet A1 (for jets) and Avgas (for smaller piston-engine planes). They have more stringent requirements than fuels used for ground use and contain specific additives to enhance and maintain properties important for fuel performance or handling.

B

Barrel

Also known as a drum, it’s a portable solution that stores 205-litres of fuel or oil.

Biodiesel

Made from vegetable oils or animal fats, it’s also called FAME (Fatty Acid Methyl Ester) diesel. Biodiesel is typically blended with petroleum diesel or used as a 100% fuel:

• B7: What you get at most UK petrol stations—7% biodiesel, 93% fossil diesel
• B20: 20% biodiesel, often used by companies trying to cut emissions
• B100: 100% biodiesel—more eco-friendly but usually needs equipment tweaks

Biofuel

A renewable fuel derived from biomass like vegetable oils and fats, offering a much cleaner burning alternative to fossil fuel. It includes biodiesel (a first-generation biofuel) and HVO (a second-generation biofuel).

Bitumen

A tar-like substance that’s present in many crude oils and produced through oil refining. It’s semi-solid at room temperature and is commonly used for paving roads and waterproofing roofs.

Blending

One of the final stages in refining where two or more components are mixed to obtain a specific range of properties in the finished product.

Boiler fuel

Used to heat water or create steam in commercial boilers – often red diesel or kerosene.

Boiling point

The temperature of a liquid at which its vapour pressure equals the external pressure.

BS 2869 (British Standard)

The official UK standard for fuels used in things like farming equipment or home heating. There are different grades depending on the use, including:

• Class A2 – Cleaner, low-sulphur fuel for machinery
• Class C1 – High-end heating oil
• Class C2 – Common heating oil for homes
• Class D – Higher-sulphur fuel for generators or heating

BSI (British Standards Institution)

The UK’s official body for setting quality and safety standards – for everything from fuel to electronics

Bunker fuel

Any diesel or fuel oil used in ships and boats. The type you need depends on your vessel. Common ones include:

• MGO – Marine Gas Oil
• MDO – Marine Diesel Oil
• IFO – Intermediate Fuel Oil
• HFO – Heavy Fuel Oil

C

Calorific value

The amount of heat energy released when a specific amount of fuel is completely burned. It measures the energy density in units like joules per kilogram or joules per cubic meter. The two main types are: gross calorific value and net calorific value.

Carbon intensity

This measures how much carbon dioxide is released per unit of fuel. The lower the number, the cleaner the fuel.

Carbon offset fuels

You still use the same regular fuel, but you pay a little extra to offset the associated carbon emissions. That money goes toward verified eco-projects like tree planting or wind farms.

Carbon reporting

This involves tracking and reporting how much carbon your business is putting out. It’s usually split into Scope 1 (direct), Scope 2 (indirect from electricity), and Scope 3 (everything else in your supply chain).

Cetane number

This tells you how easily diesel ignites. A higher cetane number means better performance and smoother running.

Class A2 gas oil

Gas oil with a maximum sulphur content of 10ppm. It falls under BS 2869 specifications and was once widely used, but it has now been replaced by EN 590 diesel.

Class D gas oil

Gas oil with a maximum sulphur content of 1000ppm (parts per million) and meets BS 2869 specifications. It’s mainly used in heat and power generation in older static engines due to its high sulphur content.

Cold filter plugging point (CFPP)

The lowest temperature at which fuel can still flow properly without affecting performance. If it gets colder than the CFPP, fuel starts to wax up, or crystalise, and clog filters, compromising performance and increasing the risk of unplanned downtime.

Compressed natural gas (CNG)

Natural gas that’s been compressed into a fuel for vehicles used as an alternative to petrol or diesel.

Contaminants

Anything you don’t want in your fuel – like water, microbes, dirt, or rust. These can mess with your engine and cause blockages.

Crude oil

A raw natural resource that comes out of the ground and is refined into things like petrol, diesel, and jet fuel. It consists of hydrocarbon deposits and other organic materials that were formed from the remains of animals and plants that lived millions of years ago.

D

Decommissioning

The permanent or temporary removal of equipment or a tank.

Density

It tells you how heavy a fuel is for its volume. Denser fuels usually give you more energy per litre.

Diesel (white diesel/DERV)

The standard diesel you get at fuel stations, also called:

• DERV (Diesel Engine Road Vehicle)
• Forecourt diesel
• White diesel
• Petrodiesel
• Road diesel
• ULSD (Ultra-low sulphur diesel)

Diesel bug

A mix of bacteria and fungi that live in water-contaminated diesel tanks. It can clog filters and damage engines.

Diesel grades

• Summer grade – Made to work better in warmer weather
• Winter grade – Flows more easily in the cold, thanks to a lower CFPP

Diesel secure (anti-theft dye)

A dye added to diesel so it’s easier to track if it gets stolen. Since the rules surrounding red diesel duty changed in 2022, more businesses are using this to protect their fuel.

Downstream

This refers to commercial activities that take place between the loading of crude oil at the export terminal and the use of oil by the end user. This includes transporting the crude oil, supplying and trading, refining crude oil, marketing, transporting and distributing the refined product output.

Downtime

The time when operations cease due to several factors, including contaminated fuel or clogged filters.

Drop-in fuel

Any fuel that can be used in your existing engine or system with no modifications needed.

E

Emissions

The gases and substances that are released into the atmosphere during the production, transportation, storage and consumption of fuels and oils – including CO₂, NOx, and particulates. Lower emissions = better for the planet.

Energy density

How much energy you get out of a certain amount of fuel. Higher density = more power per litre.

EN (European Norm)

EN standards, also known as European Standards or Euronorms are technical standards developed to facilitate trade within the European Union and ensure products, services or processes comply with the essential requirements of European legislation.

EN 15940

EN 15940 covers cleaner diesel alternatives like HVO and GTL (gas-to-liquid) which are cleaner burning alternatives to EN 590 fuels.

EN 14214

The EU standard for FAME biodiesel and uCOMe biodiesel. It sets the rules on what qualifies as proper biodiesel.

EN 590

The go-to EU standard for all road-use diesel. If you’re driving a diesel vehicle, this is probably what’s in your tank.

EN 590 diesel

Also called road diesel, EN 590 diesel is found at petrol stations and used by fleets, vans, and machinery.

EN 590 gas oil

The same as EN 590 diesel, but it’s dyed red for tax reasons. It’s also known as red diesel or rebated fuel.

Engine oils

Engine oils keep engines running smoothly by reducing heat and friction between parts. There are various types, depending on what kind of engine you have.

EURO 6

The emissions standard for vehicles in the UK and Europe. It sets strict limits on pollutants like NOx and CO₂.

F

FAME

Short for Fatty Acid Methyl Esters – FAME is the main ingredient in biodiesel. It’s great for the environment but can cause problems in engines if not managed properly (like water absorption and cold-weather issues).

Flash point

The lowest temperature at which a fuel can catch fire. Lower flash point = easier to ignite, but also more dangerous to store.

Fossil fuels

Traditional fuels like coal, oil, and gas formed over millions of years from ancient plants and animals.

Fuel additives

Extra ingredients that you can mix into your fuel to improve performance, longevity, or adapt it to new uses. They are handy for keeping engines clean or running better in tough conditions.

Fuel duty

A tax added to fuel – the amount can vary depending on what type of fuel it is – like red diesel, which is taxed less, versus regular road diesel that gets taxed fully.

Fuel oil

The heavy oils from the refining process used in power stations, industry, marine boilers etc.

Fuel polishing

Think of fuel polishing like a deep clean for your fuel. It’s a process that filters out microbes and contaminants through an advanced filtration system, so the fuel is clean and ready to use again.

Fuel testing

Fuel testing involves taking small samples from different parts of your fuel tank to check for signs of dirt or contamination that can interfere with how your equipment runs.

Fuel uplift

When fuel is pumped out of a tank – maybe because it’s not needed anymore or it needs to be moved somewhere else.

Fractional distillation

The process used to split crude oil into different fuels based on the boiling point. It’s how we get petrol, diesel, kerosene, etc.

G

Gas oil

Another name for red diesel, gas oil is marked diesel that comes in different grades and specifications and is intended for off-road use only.

Generator fuel

The kind of fuel used in backup generators – usually diesel or HVO. It’s what keeps places like hospitals or data centres running when the power goes out.

Green diesel usually refers to HVO – a renewable, cleaner-burning alternative to regular diesel.

Greenhouse gases (GHGs)

Greenhouse gases trap heat in our atmosphere, like CO₂ and methane. They’re the big players when it comes to global warming.

GTL (gas-to-liquid)

A cleaner burning type of diesel made from natural gas. It burns cleaner than regular diesel and can be used in most of the same engines without any changes.

H

H₂ (hydrogen gas)

A high-energy fuel with low greenhouse gas emissions when used in fuel cells. It can be produced from a wide range of domestic resources, including natural gas, biomass, nuclear energy, and renewables, making it a flexible and adaptable energy carrier. Its applications span transportation, electricity generation, and energy storage from renewable sources.

Heating oil

Used to heat homes or commercial premises. Variants include kerosene or domestic heating oil, used to heat off-grid homes or industrial heating oil or diesel to heat commercial buildings.

Hydraulic oil

Also called hydraulic fluid, it’s a non-compressible liquid used to transfer power in hydraulic systems – based on mineral or synthetic oil. It’s vital in many machines and equipment, serving as a lubricant, coolant and sealant in addition to its power transfer function.

Hydrocarbon

An organic compound that contains hydrogen and carbon atoms in various combinations, forming the bases for petroleum and petroleum products.

HVO (Hydrotreated Vegetable Oil)

A cleaner alternative to red and white diesel that cuts up to 90% of net CO₂ emissions. It’s made from certified waste, like used cooking oil or animal fats, and burns with way less pollution.

I

IBC (intermediate bulk container)

Those big, cube-shaped plastic tanks that are wrapped in a metal cage. They’re super handy for moving or storing large amounts of fuels.

Industrial heating oil (IHO)

A more cost-effective kind of oil used to heat places like factories or warehouses. It’s not for cars or trucks – just for keeping big spaces warm.

ISO (International Standards Organisation)

The ISO sets the global standards to ensure products, processes and services meet certain quality and safety rules. Many businesses work to ISO standards as they are universally recognised which helps ensure clarity, consistency, quality and safety across industries and countries.

K

Kerosene

A light oil used mostly for heating homes or powering jet engines. It burns clean and is pretty efficient.

Kleenburn kerosene

A cleaner burning alternative to kerosene that improves oil-fired boiler efficiency and reduces costs whilst meeting BS2869 Class C2 standards.

M

Marking

This is when a dye or chemical is added to fuel—like the red dye in red diesel—so it’s easy to tell what kind it is and how it should (or shouldn’t) be used.

MGO (Marine Gas Oil)

Fuel made for boats and ships. It’s like diesel, but with specs that fit marine engines.

Middle distillate

The fraction of petroleum liquids that are produced in the middle range of refinery distillation – which includes kerosene, gas oil and light fuel oil.

O

OEM (Original Equipment Manufacturer)

The company that originally made your equipment—like the brand of your generator or vehicle. OEM guidelines are important for making sure you use the right type of fuel or parts.

Off-road diesel

Diesel that’s dyed red to show it’s only for things like tractors or construction equipment—not road vehicles.

P

Polishing

See “Fuel Polishing” above – basically restoring dirty fuel so it’s good to go again.

Pour point

The temperature at which a fuel tends to solidify and will no longer flow freely.

R

Red diesel

Also known as gas oil, 35-second oil, tractor diesel and cherry red, is a low tax fuel that is used in untaxed off-road vehicles and machinery – it is marked red to identify illegal usage.

Renewable Diesel

Another term for HVO – renewable diesel is made from renewable materials like vegetable oils and waste fats that is significantly better for the environment than regular diesel, producing up to 90% less net CO₂ emissions.

S

Sustainable fuel

Made from renewable resources such as biomass and waste. They reduce CO₂ emissions and offer a more cleaner burning alternative to fossil fuels.

Sulphur

A natural element found in crude oil and is one of the most significant parameters used to measure the value, suitability and environmental credentials of petroleum products. Almost all crude oil derived fuels contain some level of sulphur content – high levels can damage engine components and reduce air quality.

Modern diesel fuels now contain far less sulphur and particulate content due to advancements in the refining process and legislated changes to fuel standards. 

T

Tank cleaning

As its name suggests, tank cleaning involves cleaning out a fuel tank to remove sludge, water, or any other nasty matter that can significantly reduce the stored fuel’s quality and reduce the tank’s integrity.

Tank inspection

A tank inspection is carried out by a specialist engineer who looks inside of a fuel tank (often with special cameras) to see if there are any problems like rust, sludge, or damage.

U

Ultra low sulphur diesel (ULSD)

Diesel that’s had most of the sulphur taken out to make it cleaner-burning and more eco-friendly.

V

Viscosity

The property of a fluid which determines its rate of flow. As the temperature of a fluid is decreased, its viscosity decreases and it flows more readily.

W

White diesel

Also known as DERV (Diesel Engine Road Vehicle) or road diesel, it’s the most common type of diesel fuel used in road vehicles like cars, vans, trucks, and trains. It’s a distillate of crude oil and is taxed at the full rate. Despite being often called “white diesel,” it’s actually a clear and bright amber/green in colour.