How to Compare UK Petrol and Diesel Prices Before Filling Up

Business & Money Desk 2026-10-21 07:57 4 min read

Drivers queuing at a UK supermarket petrol station forecourt to refuel their vehicles.

A lower price per litre can reduce the cost of a fill-up, but a longer drive to reach a cheaper forecourt may use up the saving. Compare the total price for the litres you need, then account for any extra distance before deciding where to stop. UK drivers can use the Competition and Markets Authority’s road fuel price information for monitoring context, while checking current local prices before setting off.

Compare the total cost, not just the pump price

A forecourt’s displayed price is usually shown in pence per litre. To estimate what you will pay for fuel, multiply the number of litres you plan to buy by the price per litre, expressed in pounds.

For example, if you buy 40 litres at 145p per litre, the fuel costs £58: 40 × £1.45. At a nearby station charging 142p per litre, the same amount costs £56.80, a difference of £1.20 before considering the journey to either station.

This calculation works for petrol and diesel. Make sure you compare the same fuel type and a similar quantity. A price difference of a few pence per litre can matter more when you are buying many litres, but the price alone does not show whether the detour makes sense.

Allow for the extra distance to a cheaper forecourt

Compare the route you would take anyway with the route to the cheaper station. The extra distance is the distance added by the detour, not the full distance from your starting point.

To estimate the detour’s fuel cost, use your vehicle’s approximate fuel economy and the price per litre. If a detour adds 6 miles and your car averages 40 miles per UK gallon, it uses about 0.15 gallons, or roughly 0.68 litres. At £1.45 per litre, that fuel costs about 99p. A £1.20 saving on a 40-litre fill-up would then be only about 21p before allowing for time or traffic.

These figures are examples, not a promise of what your vehicle will use. Actual consumption varies with traffic, driving style, vehicle load, weather and route. If you are already passing the cheaper station, the extra distance may be close to zero; if reaching it requires a separate journey, include the whole added trip.

A simple comparison is:

Fill-up cost: litres needed × price per litre.
Net saving: cost at your usual station minus cost at the cheaper station, minus the estimated fuel cost of the detour.

If the result is small, the time and hassle may outweigh the saving. If both stations are on a journey you are already making, compare their prices without charging the whole journey to the fuel stop.

How to Compare UK Petrol and Diesel Prices Before Filling Up

Estimate the litres you actually need

You do not have to compare stations using a full-tank assumption. Estimate how many litres you expect to buy, or use the amount you usually add when the warning light comes on. Then apply that same quantity to each station’s price.

For instance, a 10p-per-litre difference saves £4 on 40 litres, but only £2 on 20 litres. The comparison is most useful when the amount is consistent: changing both the station and the quantity makes it harder to see what the price difference is worth.

Check the pump display as you arrive. Prices can change, and an online listing or published average may not match the price at that forecourt when you fill up. Also check that the price applies to the fuel grade you use; premium petrol and other grades may cost more than standard unleaded.

Where to check UK fuel prices

The Competition and Markets Authority (CMA) publishes road fuel price monitoring publications and related data through its collection on GOV.UK. It is useful for understanding the CMA’s monitoring of UK road fuel prices and for finding official publications, but a national figure should not be treated as the price at every forecourt or in every town.

The CMA has also provided guidance on fuel finders where available. Check its current road fuel publications and guidance for information about finding or comparing local prices. Before making a special trip, confirm the current price with a local fuel finder or the forecourt itself if possible, and check the pump when you arrive.

Local prices can vary by area, station and fuel type. A nearby supermarket forecourt, motorway service station and independent site may not charge the same price, and one comparison may not represent the wider local market. Treat published averages as context, then compare the specific stations on your route.

A quick check before you set off

Identify the fuel type and roughly how many litres you need.
Compare current prices at nearby stations on or near your route.
Calculate the fuel cost at each station using litres × price per litre.
Estimate the fuel used by any extra distance and subtract that cost from the apparent saving.
Check the price at the pump before filling up.

The best choice depends on the current local price, the amount you need and the route you would otherwise drive. Recheck those details when you next fill up: a national monitoring figure can provide context, but only the price and detour for the stations you are considering can show your likely saving.

Source: Competition and Markets Authority via GOV.UK

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The fill-up examples are calculations from stated litres and prices; local pump prices and vehicle fuel use can differ.

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