How to Compare UK Petrol and Diesel Prices Before Refuelling

A national average can help you judge whether UK petrol or diesel prices are moving, but it cannot tell you what a nearby forecourt charges. Check current local prices before setting off, then use your vehicle’s tank capacity and the pump price to estimate a fill-up. That gives you two useful checks: whether a station’s price is reasonable in context, and roughly what buying the fuel you need will cost.

Check current prices in your area

RAC Fuel Watch publishes UK average prices for petrol and diesel, alongside commentary on price movements. Check the latest figures and the date displayed on the RAC Fuel Watch page when you use it. Averages change, so a figure without a date may no longer be useful.

Treat the RAC average as context, not a quote for your local station. It describes an average across the UK; prices can differ between nearby forecourts, and a price listed online or in an app may not reflect a later change at the pump. Confirm the displayed price when you arrive.

To compare options, look up several stations near your home, workplace or planned route using a local fuel-price service if available. Compare the same fuel type and, where relevant, the same grade: petrol and diesel prices are not interchangeable. Check when each listing was updated and whether the station is open, then use the forecourt’s pump price as the final check before filling.

A comparison is most useful when it covers stations you could visit as part of a journey you already plan to make. A cheaper listed price farther away may not reduce your total cost once the extra trip is taken into account.

Why prices differ between forecourts

Pump prices reflect fuel costs and local conditions. Wholesale fuel costs can change, while delivery, operating and property costs vary by site. Competition also matters: a station near several rivals may price differently from one with fewer alternatives.

As a result, two forecourts in the same town can charge different prices, and the national average can sit above or below what you see locally. Stations may also update prices at different times, so a comparison is only as current as the information behind it. If listings have different update times, treat a small apparent price gap cautiously and check the pump price before buying.

Compare like with like: petrol against petrol, or diesel against diesel, and note the price per litre. If you are considering a premium grade against standard fuel, check that the comparison suits your vehicle and driving needs; otherwise, the apparent price difference may not be a useful guide to your options.

Estimate the cost of a fill-up

UK forecourt prices are usually shown in pence per litre. Convert the pump price into pounds per litre, then multiply by the litres you expect to buy:

Estimated cost = price per litre in pounds × litres bought

For example, at 150p per litre, the price is £1.50 per litre. Buying 40 litres would cost £60: £1.50 × 40. This is a checked arithmetic example, not a claim about today’s local price.

A full tank may cost more or less than an estimate based on a particular number of litres, depending on how much fuel is already in the tank. For a more useful estimate, check your vehicle handbook or manufacturer information for tank capacity and work out how many litres you expect to need. Tank capacity indicates the size of a full tank; it does not tell you how much fuel you need to buy for a top-up. The final charge depends on the amount dispensed and the price shown at the pump.

Decide whether a cheaper station is worth the detour

Calculate the likely saving across the litres you plan to buy, then weigh it against the extra journey. For instance, a difference of 5p per litre on 40 litres saves £2 before accounting for the detour.

Extra distance can use up some or all of that saving through fuel and time. The outcome depends on your vehicle, route and traffic, so there is no single distance that makes a detour worthwhile for everyone. Check whether the cheaper station is on a journey you already need to make, and compare the likely saving with the cost of travelling out of your way.

If the saving is modest, a convenient nearby forecourt may be the sensible choice. Check prices again before travelling: a listed price can change, and a long detour based on stale information may erase the benefit.

Source: RAC