How to Compare UK Petrol and Diesel Prices Before You Fill Up

Before you fill up, compare prices at nearby forecourts and use your vehicle’s tank size to estimate the bill. RAC Fuel Watch publishes UK average petrol and diesel prices, but those figures are a national benchmark, not a quote for a station near you. Check the page’s displayed update date and compare it with local prices before deciding where to stop.

Check current petrol and diesel prices near you

Start with RAC Fuel Watch to see the latest UK average for petrol and diesel and its commentary on price movements. Note the date shown on the page: fuel prices change, so an undated figure can give a misleading impression of what drivers are paying now.

Treat the average as a reference point. A station’s pump price may be higher or lower, and prices can differ even between forecourts in the same area. To find a local price, check current station listings or price information available for your area, then confirm the displayed price when you arrive.

A useful comparison should use the same fuel type and unit: pence per litre for petrol against petrol, or diesel against diesel. Also check that the listing is recent. If you cannot tell when a local price was last updated, treat it as an estimate rather than a confirmed pump price.

Why prices differ between forecourts

There is no single price that applies to every UK filling station. Local competition, the station’s location and its operating costs can all contribute to differences. A forecourt on a busy route or in a less competitive area may charge a different price from one a short distance away.

Prices can also change over time as wholesale costs and other factors move through the supply chain. RAC Fuel Watch provides commentary on price movements, but a change in the national average does not mean every local station changes its price by the same amount or on the same day.

For that reason, compare the actual prices you could use rather than assuming the cheapest option will be the same everywhere. A national average helps with context; the local pump price determines your bill.

Estimate the cost of filling your tank

To estimate a fill-up, multiply the litres you plan to buy by the price per litre. Convert pence to pounds by dividing by 100:

Cost in pounds = litres × price in pence per litre ÷ 100

For example, if you buy 40 litres at 150p per litre, the calculation is 40 × 150 ÷ 100 = £60. This is an illustration, not a current UK price. Your actual cost depends on the price at the pump and how much fuel your vehicle needs.

Use the amount you expect to add, not automatically the tank’s full capacity. If the tank holds 50 litres but already has about 10 litres in it, a near-full top-up would be roughly 40 litres. The gauge is not a precise measuring tool, so treat the result as a budget estimate.

A small per-litre difference can be put into pounds the same way. For a 40-litre purchase, a 2p-per-litre difference works out to 40 × 2 ÷ 100 = 80p. Whether that is worthwhile depends on the extra distance and time needed to reach the cheaper station.

Decide whether a detour is worth it

Before driving out of your way, compare the possible saving with the extra journey. Work out the price difference per litre, multiply it by the litres you expect to buy, then consider the additional distance, fuel use and time. The saving may shrink or disappear if the detour is long or traffic is heavy.

For instance, an 80p saving on a 40-litre fill-up is the maximum price advantage in the example above, before accounting for the detour. A driver who is already passing the cheaper forecourt may find it worthwhile; making a separate journey for the same difference may not be.

Check nearby options before changing your route. If a station’s price is based on an old listing, call ahead where practical or verify the sign on arrival. A listed price is not a guarantee that the pump price will still match it.

Use averages for context and local prices for the decision

RAC Fuel Watch can help you understand the broader direction of UK petrol and diesel prices. For a refuelling decision, pair its latest dated averages with recent prices for nearby forecourts, then estimate the cost using the litres you actually expect to buy.

The practical next check is the RAC page’s current update date alongside local station prices on the day you plan to fill up. That keeps a national trend in perspective and helps you judge whether a nearby price difference is worth a change of route.

Source: RAC