Motorway Fuel Stops Cost UK Drivers Up to £14 More a Tank, CMA Reveals

• Filling up at a motorway services can cost up to 26p a litre more for petrol and 17p a litre more for diesel than the UK average forecourt price, according to the Competition and Markets Authority.
• On a 55 litre tank, that works out at just over £14 extra for petrol and more than £9 extra for diesel, simply for choosing the wrong forecourt.
• Retailer margins climbed to 10.7p a litre in March 2026, up from 10.3p in February, and the CMA’s most recent update in August 2026 says historically high margins remain a concern.

Drivers who fill up without leaving the motorway are paying a premium most of them never see broken down in pence and pounds. The Competition and Markets Authority, the government body that has been monitoring the road fuel market from 2023 onward, publishes regular data comparing what different types of forecourt charge for the same litre of petrol or diesel. Its most detailed breakdown, the Enhanced Road Fuel Monitoring Report, put the average motorway premium at up to 26p a litre for petrol and up to 17p a litre for diesel compared with forecourts off the motorway network.

Multiply that by a 55 litre tank, the size fitted to most family cars and small SUVs, and a motorway fill costs just over £14 more for petrol drivers and more than £9 more for those running on diesel, according to the CMA’s own worked figures. For a family topping up twice on a return trip to the coast, that is close to £30 spent purely on the convenience of not leaving the carriageway.

The CMA has continued to flag the issue after that report was published. In an update on 18 August 2026, the regulator said margins had stayed historically high, a finding it linked partly to what it calls passive pricing strategies among retailers, where forecourts track each other’s prices upward rather than compete on cost. The average margin taken by all fuel retailers combined rose from 10.3p a litre in February 2026 to 10.7p in March, matching the 10.7p average margin recorded across the whole of 2025.

The people most exposed to this gap are not occasional motorway users but the drivers who spend the most time on the network: long distance commuters, delivery drivers, haulage operators and anyone making a family holiday trip along a motorway corridor. A driver commuting 120 miles a week on a motorway and topping up once at a services station rather than at a local forecourt could be paying an extra £14 a week on petrol alone, which comes to well over £700 a year before any change in the underlying pump price. For a household running two cars, both regularly using motorway services out of habit rather than necessity, the same yearly cost can effectively double across the two vehicles combined.

Where the extra money actually goes

Motorway services forecourts are almost always run under exclusive contracts with National Highways or the equivalent devolved body, which limits how many operators can compete for the same stretch of tarmac. Away from a motorway, a driver might have three or four filling stations within a short detour and can simply drive to whichever is cheapest. On the motorway network, the operator holding the site licence knows the driver is unlikely to leave the carriageway to save a few pence, and prices are set accordingly.

The CMA’s data shows this problem is not confined to motorways. Even away from them, the gap between supermarket forecourts and other retailers reached up to 8p a litre for petrol and 11p a litre for diesel, worth roughly £5 and £6 respectively on a 55 litre tank. And within a single local area, the regulator found a price range of up to 16p a litre for petrol and 17p a litre for diesel among forecourts a ten minute drive apart, a gap worth up to £9 a tank to a driver willing to check before filling up.

None of this is new behaviour. What has changed is that the CMA is now measuring it every month and naming the scale of it in pence and pounds, rather than leaving drivers to guess whether a particular services station is expensive or simply typical. The regulator’s road fuel monitoring programme was set up after its 2023 market study into the fuel sector found that margins had risen well above their historic range, and it has kept publishing figures on a rolling basis to see whether that gap closes.

Background pump prices add urgency to the numbers. RAC Fuel Watch data put the UK average diesel price at 198.32p a litre and petrol at 173.6p a litre on 25 September 2026, with diesel up 39.3 per cent from the end of February. Against that backdrop, a driver paying the full motorway premium on top of an already higher underlying price is losing more in cash terms than the same percentage premium would have cost a year ago.

Can you avoid it

The single most effective step is to fill up before joining the motorway rather than at a services station partway through the trip. Most motorway services are spaced roughly every 25 to 30 miles, so a full tank taken on at the start of a trip will usually cover a return leg without needing a top up at a premium site.

Free price comparison apps and websites, including PetrolPrices and the RAC’s own fuel price checker, let drivers see live prices at stations along a planned route before they set off, including which supermarket forecourts sit just off a motorway junction. Supermarket fuel, according to the CMA’s own figures, is reliably among the cheapest available, and several supermarkets link fuel discounts to a minimum in-store spend, which can offset some of the pump price on a routine shopping trip.

Fuel apps that use live price feeds rather than user submitted prices tend to be more accurate for planning ahead, as forecourts can change prices more than once in a day. Checking prices the evening before a long drive, rather than relying on memory of what a station charged weeks earlier, avoids the biggest single mistake drivers make, which is assuming a familiar forecourt is still competitively priced.

Loyalty schemes run by supermarkets and some fuel card providers can also narrow the gap, especially for drivers who fill up regularly at the same chain. For anyone who drives for work and can claim mileage, keeping receipts from the cheapest available forecourt rather than the nearest one adds up over a tax year, as business mileage rates are calculated on the assumption of average, not premium, fuel costs.

A short detour off a motorway junction, rather than pulling straight into the services car park, is often enough on its own. Many junctions have a supermarket or independent forecourt within a mile or two of the slip road, and the CMA’s figures suggest that short diversion is worth several pounds a tank on its own. Setting a fuel app to alert when the tank drops below a quarter full, rather than waiting until the warning light comes on at an inconvenient point on the motorway, gives a driver enough notice to plan that detour rather than being forced into the nearest services out of necessity.

Where a motorway stop is unavoidable, such as on a long haul trip where a full tank will not last the whole route, filling only enough fuel to reach the next non-motorway station, rather than filling to the brim, limits how much of the tank is bought at the inflated price.

Sources: Competition and Markets Authority, Enhanced Road Fuel Monitoring Report, published 01/05/2026 (data to April 2026); Competition and Markets Authority, road fuel market monitoring update, published 18 August 2026; RAC Fuel Watch, UK average petrol and diesel prices, 25 September 2026.