What sets the price on your forecourt

A price board tells you one number. Behind it sit tax, the type of forecourt, the road you are on and a wholesale market far away. Here is what each one does to your bill, starting with what the number on the board actually means.

Reading the board

Prices are in pence per litre. 197.9p means £1.979 for every litre. Fill fifty litres at that price and you hand over £98.95. A penny on the board is fifty pence on the same tank. Small numbers, real money.

Supermarkets

On this site, supermarket forecourts typically show lower prices than the rest. The supermarket page lists today's prices at their forecourts. It is a pattern in the data, not a rule, so check your own town page before you assume.

Motorway services

Once you are on the motorway, your choice shrinks to the services along the route. Competition is thin, and service areas run on different costs. The motorway page puts today's gap in pence. Choose your stop before the fuel light chooses it for you.

Tax

A big slice of the price is tax — fuel duty plus VAT. A change in duty moves the board overnight, whatever crude oil is doing. That is why the policy calendar matters as much as the oil price.

When every board moves at once

If every forecourt in town goes up together, the cause is not local. Diesel is bought on a market the UK shares with the rest of Europe. With Russian diesel off the table, that market leans on refined cargoes from the Gulf, and those have become scarcer and dearer since the Middle East crisis. Europe also refines less than it did and buys in a growing share of its finished diesel. Trouble on the sea route shows up on your board within weeks.