Motorway fuel prices

How much more you pay

Motorway service area forecourts consistently price above the surrounding area.

A realistic worked example. Suppose the services are charging 15p a litre more than a supermarket four miles off the junction. Filling 50 litres at the services costs £7.50 more. The eight-mile round trip to the supermarket uses roughly 0.9 litres of fuel — under £1.30 — and perhaps ten minutes. You are clearly better off leaving.

Why service areas charge more

It is not arbitrary, though it is certainly opportunistic.

• Site costs are genuinely high. Service areas operate under government requirements: open 24 hours a day, every day, with free parking for two hours and free toilets and drinking water. Those obligations cost money that a forecourt on a local high street does not carry.
• The market is captive. A driver who is genuinely low on fuel has no alternative within range. Ordinary price competition does not function when the customer cannot leave.
• Many drivers are not paying. A large share of motorway fuel goes into fleet and business vehicles on a fuel card. Those drivers have little incentive to detour, which weakens price pressure further.

The CMA examined the road fuel market and found competition working poorly in places; the open price-reporting scheme that underpins this site came out of that work. But there is no cap on what a service area may charge.

Is the detour worth it?

The arithmetic is simple enough to do in your head. Multiply the price gap in pence by the litres you are buying, then divide by 100 for pounds saved. Against that, a ten-mile round trip in a 40mpg car costs about £1.60 in fuel.

For a full tank the detour wins almost every time. It stops being worth it when you are adding a small top-up, when the alternative is more than about five miles off the junction, or when you are genuinely short of time. And if the fuel light is on and the next junction is fifteen miles away, pay the premium — running out on a motorway is expensive and dangerous in ways no price gap justifies.

Planning fuel stops on a long drive

The reliable approach is to decide where you will fill before you set off rather than when the gauge gets low. Check the map along your route, pick a supermarket forecourt near a junction roughly where you expect to need fuel, and treat the services as the fallback rather than the plan.

On long cross-country runs it is also worth knowing where prices rise. Fuel gets markedly dearer in the South West peninsula beyond Exeter, in mid and west Wales beyond Swansea, and in the Scottish Highlands beyond Stirling. Filling before those stretches saves more than any junction-level decision.