Drive between two towns twenty miles apart and you can watch the price on the forecourt sign swing by 20p a litre or more. Most drivers have a theory for why: it's the brand, it's how remote the area is, it's just "wherever you are."
We wanted to find out what's actually going on. So we took every Great Britain petrol station we have live pricing for — 7,160 for petrol, 7,186 for diesel (England, Scotland and Wales; Northern Ireland uses separately-licensed postcode data we've excluded from this analysis) — and built a model that predicts what a station should charge based purely on its structural situation: how much competition it has nearby, how far it sits from the refineries and import terminals that supply it, the wealth of the surrounding area, and how densely populated the region is.
Then we looked at where reality and prediction disagree, and by how much.
Regional price levels
What drivers are actually paying, station by station.
Relative to what's structurally expected
Same stations, coloured by the residual — actual price minus what a model predicts from location, competition, supply-chain distance, deprivation and population density alone. Teal = priced almost exactly as expected.
The Obvious Explanation Isn't the Real One
Before running the numbers, our working theory was that location would dominate — that rural stations, cut off from competition and further from the refineries and coastal terminals that supply them, would be the story.
That turned out to be true, but nowhere near as true as we expected. Once we actually measured it, one factor beat every other structural explanation combined, by a wide margin:
Whether a station sits on the motorway.
Motorway services stations are, on average, 16.6p a litre more expensive for petrol and 21.0p more for diesel than every other station in the country. On a 55-litre tank, that's an extra £9.13 for petrol or £11.55 for diesel — every single time you fill up at a services rather than pulling off at the next junction.
That's not a small effect buried in the noise. In our model, it's dramatically more predictive of price than competition, supply-chain distance, local deprivation, or population density — all the things you'd normally reach for first.
Why Motorway Services Get Away With It
The mechanics aren't complicated once you think about it: a motorway services station has a genuinely captive audience. You can't easily leave the motorway, compare three forecourts, and come back. The next opportunity to refuel might be fifteen minutes and one junction away — by which point you've either bought the fuel or you haven't.
Compare that to a normal high-street station, competing head-on with two or three others within walking distance and every one of them visible to a driver deciding where to turn in. That competitive pressure is real in our model too — the number of nearby competitors is one of the strongest remaining factors once motorway status is accounted for — it's just that no ordinary competitive pressure comes close to what a captive motorway audience allows.
What's Left, Once Motorway Services Are Set Aside
Strip motorway services out of the picture, and the remaining differences are real but far more modest. Rural stations (excluding motorway services) average roughly 2-3p a litre more than urban ones — a genuine but much smaller gap than the motorway effect, and one that interacts with how much competition a station actually has nearby, not just its postcode.
The second map above shows this directly: colour is the residual — how far a station's real price sits from what the model expects once competition, deprivation, population density and supply-chain distance are all accounted for. Motorway services light up red immediately. But plenty of ordinary stations still surprise the model in both directions.
Skerries Co-operative Society on Shetland is a good example of the map working as intended — an isolated island station, charging noticeably more than almost anywhere else in the country, and coming out 52.9p above what the model expects for petrol (47.2p for diesel) even after accounting for its remoteness.
Distance from the mainland isn't the only thing that can surprise the model, though. Harrisons Esso in Whitby, North Yorkshire — a real seaside town, not remote by UK standards — charges 23.2p less than its situation would predict, a reminder that the map isn't just finding "expensive and remote", it's finding genuine local pricing decisions in both directions.
The Takeaway
If you're trying to avoid overpaying for fuel, the single most useful rule from this analysis is the simplest one: avoid filling up at motorway services if you can help it. Pulling off at the next junction, or filling up before you join the motorway at all, will save you more than any amount of brand-shopping between two ordinary forecourts.
Beyond that, competition is still your friend — a station with several visible rivals nearby has far less room to overcharge than an isolated one. And, as the second map shows, a small number of stations, in both directions, charge meaningfully more or less than their situation would suggest. Worth knowing before your next fill-up, wherever you are.
What's Next
This analysis explains why prices differ right now, station by station. The natural next question is whether they're about to change — and that's what we're building next, using crude oil and wholesale futures markets instead of location and competition.
Early findings are already interesting on their own. Fuel prices don't fall the way they rise: when wholesale costs jump, pump prices follow within about a day; when wholesale costs fall, that saving takes much longer to show up, if it shows up in full at all — the "rockets and feathers" effect, now visible clearly in UK station-level data. We can even put a rough number on the lag: after a wholesale cost shift, it typically takes about a week for half of that gap to close at the diesel pump (faster for petrol — nearer four days). And competition doesn't just keep a station's everyday price lower — it also slows down how fast that station passes on a wholesale rise.
We won't be turning this into a "prices will definitely move" tool — no forecast is right every time, and we'd rather stay quiet than cry wolf. The plan is to only alert you when the signal is unusually clear, so a notification actually means something. Get notified when it launches, or set a free price alert for your local stations right now.