Fuel and gas glossary
Plain-language definitions for the terms behind fuel prices, from octane ratings to price caps, each linked to where you will see it in FuelTheGuide.
Start with the basics
Octane rating
A measure of how well petrol resists knock. It explains why grades such as 95 and 87 are not directly comparable.
Read the full entryNational average price
The average retail price of a fuel across a whole country. It is the price figure every country on our site shows.
Read the full entryGovernment-fixed price
A pump price set by a government and changed on a schedule, which is why some countries' prices stay flat for weeks.
Read the full entryGuides for learning more
Longer reads that connect these terms to the way fuel prices work. Each guide links back to the entries it uses.
How to compare fuel prices between countries
Why the same litre isn't the same price: currencies, units, grades and taxes.
What makes up the price at the pump
Crude oil, refining, distribution and taxes, and why the split differs by country.
Petrol or diesel: which costs less to run?
Price per litre is only half of it. Fuel use, taxes and distance decide.
Why some countries have very cheap fuel
Subsidies, price caps and fixed prices, and what they mean for travellers.
All terms, A to Z
The octane number on US and Canadian pumps. It is the average of RON and MON.
On our site: Shown in US grade names, such as Regular 87.
Prices updated by hand for countries without automatic collection. They may be out of date.
On our site: Labelled on prices, and you can hide them.
A diesel component made from vegetable oils or animal fats and blended into regular diesel in many countries.
The main international benchmark for crude oil prices. Pump prices tend to follow it with a delay.
A measure of how readily diesel ignites under compression. A higher number means smoother combustion.
Compressed natural gas, stored under pressure and used as a vehicle fuel. It is often sold by weight, not volume.
On our site: Shown where a country publishes it.
A fuel that ignites under compression, used in trucks, vans and many cars.
On our site: Diesel and premium diesel on separate grades.
A fixed tax per litre or gallon of fuel, charged before VAT. It can be a large share of the total when pre-tax prices are low.
Petrol blended with 10% or up to 85% ethanol. E10 needs a compatible vehicle.
On our site: E10 is its own grade where published.
The price of one currency in another. We use it to show every fuel price in your chosen currency.
On our site: The currency picker.
Government support that keeps pump prices below the market level.
On our site: Subsidised markets are labelled.
Two names for the same fuel: gasoline in North America, petrol in most other English-speaking countries.
On our site: We use the local name for each country.
A pump price set by a government or regulator and changed on a schedule, which is why some countries' prices stay flat for weeks.
On our site: Labelled, with how often it changes.
A fuel type or octane class sold at the pump, such as 95, 98 or Premium.
On our site: The fuel picker.
A refined fuel used for heating and lighting, and in a further refined form as jet fuel. A few countries sell it at the pump.
Liquefied petroleum gas, a mix of propane and butane used as a car fuel. It is usually much cheaper per litre than petrol.
On our site: LPG appears as its own grade.
The average retail price of a fuel across a whole country, not the price at one station.
On our site: Every price on our site.
A measure of how well petrol resists knock. A higher number resists it better.
A maximum price for fuel set by a government.
Research Octane Number: the octane number used in Europe, the UK, Australia and much of Asia, such as 95 or 98.
On our site: Used in most grade names outside North America.
Why the same fuel carries different octane numbers depending on the country. RON is used in most of the world; AKI in the US and Canada.
Our two comparison groups for petrol. Each country's usual grade is standard, and higher-octane grades are premium.
On our site: Comparison groups in the explorer.
A country where heavy subsidies keep fuel prices below market levels. We label these so you can filter them out.
On our site: A label and a filter.
A US gallon is 3.78541 litres. An imperial gallon is 4.54609 litres.
On our site: The unit picker.
Value-added tax is added to fuel prices in most countries. Rules differ widely, and the US uses state and federal fuel taxes instead.
The percentage difference between this week's average price and last week's.
On our site: Shown next to every price.
The dataset refreshes once a week, and every figure shows the date of its last update.
On our site: Every table shows the date.