How to Compare Fuel Prices Before a UK Journey

Business & Money Desk 2026-10-26 11:30 4 min read

Drivers filling up with petrol at a busy London petrol station forecourt.

Planning a UK drive? Checking current petrol and diesel prices near your route, then allowing for your car’s real-world fuel economy, can help you estimate the cost. A cheaper pump may not save money if reaching it adds a long detour, and prices can vary by station, location and date.

Where to check current UK fuel prices

The UK Government’s road fuel prices guidance points drivers to information about fuel prices and the Competition and Markets Authority (CMA). Check the CMA’s fuel-finder information for help comparing local prices, then confirm a station’s price as close as practical to your journey. RAC Fuel Watch also publishes information and analysis about UK petrol and diesel prices.

Treat any listed price as a snapshot: it can change, and the price at one station may not match another nearby. Check that you are comparing the same fuel type, and look for the date or other indication of when the price information was last updated. Do not rely on an undated national figure to predict what you will pay locally.

Before setting off, compare stations near your starting point, destination and planned route. If a price listing is unclear or seems out of date, check directly with the station or use another current listing. If you need fuel during the trip, prices along the route matter more than a low price far away from it.

Estimate fuel cost using your car’s mpg

For a vehicle with fuel economy in miles per gallon (mpg), use this calculation:

Journey distance in miles ÷ vehicle mpg × current price per litre × 4.546 = estimated fuel cost

The factor 4.546 converts one UK gallon into litres. This version assumes mpg is measured in UK imperial gallons. If your vehicle’s figure uses US gallons, convert it to UK mpg before using this formula.

Use the distance for the journey you expect to drive, including meaningful route changes or stops. For a return trip, include both directions. The result is an estimate of fuel consumed, not a guaranteed bill: traffic, speed, hills, weather, vehicle load and driving style can all affect consumption.

Use your vehicle’s real-world efficiency if you have it, such as a figure based on recent journeys. A quoted or dashboard figure may differ from what the car achieves on your route. Petrol and diesel vehicles can also have different mpg, so use the figure for the vehicle and fuel you will actually use.

How to Compare Fuel Prices Before a UK Journey

Worked example: estimate the cost of a 150-mile drive

Suppose a car averages 40 UK mpg, the journey is 150 miles, and the current local price is 150p per litre (£1.50). The calculation is:

150 ÷ 40 × £1.50 × 4.546 = about £25.57

That estimate assumes the car achieves 40 mpg throughout the trip and the price remains £1.50 per litre. If your route is longer, or your real-world mpg is lower, the cost will rise. Replace both example figures with current information for your vehicle and journey.

Check whether a cheaper station is worth the detour

Compare the saving at the pump with the cost of getting there. A station with a lower price per litre might require extra miles, add time, or take you away from your planned route. Those extra miles use fuel too.

Estimate the detour fuel cost with the same formula, using the added distance and your vehicle’s real-world mpg. Then compare that amount with the expected saving from filling up at the cheaper station. For a short top-up, a small price difference may be outweighed by even a modest detour; a larger fill or a bigger price gap can change the calculation.

Allow for the full extra route, including the drive back to your original route if needed. Consider time and convenience as well as fuel: a cheaper stop may still suit you, but the pump price alone does not show the whole cost.

A quick checklist before you set off

Check current petrol or diesel prices close to your route using the CMA’s fuel-finder information and RAC Fuel Watch.
Check when the price information was updated and confirm the station sells the fuel your vehicle needs.
Use your expected route distance and realistic vehicle mpg to estimate fuel use.
Convert UK gallons to litres in the calculation by multiplying the fuel used in gallons by 4.546.
Include any extra miles to reach a cheaper station before deciding whether the saving is worthwhile.

Prices and route conditions can change. Recheck the station price and your route before departure, especially if the journey is planned for a later date.

Source: UK Government

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This guide explains how to compare local fuel prices and estimate journey costs; station prices and real-world fuel economy can change.

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