Not sure about the numbers? Tap the closest match — you can tweak them after.
Fill cost = litres needed to top up × pump price. Trip cost = the fuel you burn driving there and back (real road distance ÷ your mpg × pump price). True cost is the two added together, so a cheap-but-far station is judged fairly against a dearer one nearby. Road distances are real routes from OSRM on OpenStreetMap data; if routing is unavailable the app estimates from straight-line distance and says so.
Every UK petrol station reports its prices to the government's Fuel Finder scheme, and a small computer here fetches the whole feed every hour. Prices are retailer-reported: most change daily, a few sit unconfirmed for weeks, and anything not confirmed for a fortnight wears an age badge in the results so you can weigh it yourself.
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