Anyone who has filled up at a motorway service station knows the feeling: the price on the board is always higher than at the supermarket down the road. But how much higher, and is it worth the detour to avoid it? Using patterns tracked by the RAC Fuel Watch and AA Fuel Price Report, this piece sets out the real size of the gap, what it costs on a typical tank, and when paying the motorway premium is still the sensible choice.
Why forecourts on the motorway charge more
Motorway service areas operate under different economics to a supermarket forecourt. Sites are typically leased on long contracts to a small number of operators, footfall is captive rather than competitive, and running costs — rent, staffing, 24-hour opening — are higher. Because drivers on a motorway cannot simply pull into a rival station a mile away, there is less competitive pressure to keep prices down.
Supermarkets, by contrast, use fuel as a way to bring shoppers through the door. Tesco, Sainsbury's, Asda and Morrisons have historically priced fuel close to cost, or even at a loss on some lines, because the real margin comes from the weekly shop. This is a structural difference, not a temporary blip, and it shows up consistently in AA and RAC data across different fuel-price cycles.
The RAC has published analysis for several years describing a persistent 'motorway premium', and its findings have generally shown motorway unleaded and diesel priced well above the UK average, and further still above supermarket-only averages. The gap moves with wholesale prices but rarely closes.
The size of the gap, in pence per litre
Based on typical patterns reported by RAC Fuel Watch and the AA over recent years, supermarket petrol has often averaged around 135–140p a litre, while motorway service station petrol has averaged closer to 160–165p a litre — a gap in the region of 20–25p a litre. Diesel tends to show a similar or slightly wider gap, partly because diesel volumes at motorway sites serve a lot of commercial traffic with less price sensitivity.
These are not one-off spikes. The AA Fuel Price Report has repeatedly flagged motorway forecourts as the most expensive category of site it tracks, ahead of both supermarkets and other independent or branded forecourts off the motorway network. The ranking rarely changes even when wholesale costs and fuel duty are stable, which suggests the gap is built into the business model rather than driven by short-term supply shocks.
What that means for a real fill-up
Put in cash terms, a 55-litre family car tank filled with petrol at a 25p/litre premium costs an extra £13.75 compared with filling at a supermarket. Do that once a month and it adds up to roughly £165 a year — enough to cover several return trips or a decent chunk of car insurance. For diesel drivers covering higher motorway mileage, such as company car users or small business owners, the annual difference can run higher still.
This does not mean motorway fuel is bad value in every case. If the alternative is running the tank dry, taking a lengthy detour, or arriving late for a work commitment, the premium buys convenience and certainty. The economics only turn against the driver when motorway fuel becomes a habit rather than an emergency.
Closing the gap: practical tactics
The most reliable saving is planning ahead of a long journey rather than relying on motorway services for a full tank. Filling up close to full before joining the motorway, and only topping up services with the minimum needed to get to the next supermarket or off-motorway forecourt, limits exposure to the premium.
A few habits make a consistent difference over a year of driving.
- Fill to near-full before a motorway trip rather than relying on services en route
- Use a fuel-price app or DESNZ weekly road fuel price data to compare nearby supermarket and off-motorway prices before a journey
- Treat motorway services as a top-up option, not a main fill, unless the tank is genuinely low
- For regular long-distance drivers, check whether a fuel card or loyalty scheme narrows the gap at specific chains
The takeaway
The supermarket-versus-motorway gap is real, persistent and structural rather than a short-term pricing quirk, typically running at 20–25p a litre according to RAC and AA tracking. On a full tank that is worth avoiding when practical, but the premium buys genuine convenience when time or fuel is running short. The sensible approach is to treat motorway fuel as a top-up, not a default, and to plan fill-ups around it.
