Motorway vs supermarket fuel prices
The motorway premium in pence per litre, the break-even detour distance, and how to plan fuel stops on a long drive.
6 min read · Written by Sam Richards · Last reviewed 2026-08-17
Key takeaways
- Motorway services typically charge 15-20p per litre more than a nearby supermarket — around £9-11 on a 55-litre fill.
- A detour is usually worth it if the cheaper station is within roughly five minutes of the junction.
- Filling before you join the motorway is almost always cheaper than filling on it.
The size of the motorway premium
We measure the gap continuously between stations flagged as motorway service areas and everything else. It has consistently sat in the mid-teens of pence per litre, and it is wider for diesel than petrol at many sites.
The reasons are structural rather than opportunistic: service areas pay high rents, are required to stay open 24 hours, and serve drivers who have limited alternatives once they are on the road.
When a detour pays for itself
Work it out from the size of your fill rather than a rule of thumb. A 50-litre fill at a 17p saving is £8.50; a detour of four miles each way in a 45mpg car costs roughly 80p of fuel plus around ten minutes.
That maths comfortably favours leaving the motorway if the cheaper site is close to the junction. It stops working if you are only topping up 15 litres, if the detour runs through town traffic, or if the time matters more than the money.
- Big fill, short detour — leave the motorway.
- Small top-up, long detour — stay on it.
- Running low with no plan — pay the premium and buy only what you need to reach a cheaper site.
Planning fuel stops on a long drive
The reliable approach is to fill before you join. Supermarket forecourts near the start of your route are usually the cheapest fuel you will see all day, and a full tank on a modern car covers 400-500 miles.
If you need a second stop, look one junction ahead rather than at the next services — many A-road and retail-park sites sit within a mile of motorway junctions and price against local competition rather than captive traffic.
Frequently asked questions
How much more is fuel at motorway services?
Typically 15-20p per litre more than a nearby supermarket forecourt, which is roughly £9-11 extra on a 55-litre fill.
Is it worth leaving the motorway for cheaper fuel?
Usually yes for a full tank if the cheaper station is within about five minutes of the junction. For a small top-up the saving rarely covers the detour.
Why is motorway fuel so expensive?
High site rents, 24-hour staffing obligations and drivers with few immediate alternatives all push prices up. Competition between service areas is weak because you cannot easily compare them mid-journey.
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Prices come from the UK Government's Competition and Markets Authority (CMA) open fuel price scheme and refresh throughout the day. Figures older than seven days are excluded.