How WorthThePump Works
We go further than other fuel price apps. Instead of just showing you the cheapest station, we calculate whether driving there will actually save you money — for your car.
Three steps to your answer
Enter your number plate
We look up your vehicle via the DVLA VES API — make, fuel type, engine size, CO2 emissions. From this we derive your real-world MPG automatically.
Confirm your fill amount and radius
Tell us roughly how much you typically spend on fuel (or select 'fill it up'). Choose a search radius of 1–20 miles.
See your exact savings on the map
We fetch live prices from every station in your radius and run the calculation for each one. Green pins are worth the trip. Red pins are false economies.
The calculation
THE FORMULA
Example
You drive a Ford Focus (40 MPG real-world) and fill 45 litres. The nearest Asda is 3 miles away and 8p/litre cheaper than the local Shell. Gross saving: £3.60. Round-trip detour: 6 miles. Extra fuel used: 0.15 litres × 145p = £0.22. Net saving: £3.38. Worth it!
How we work out your MPG
Manufacturer MPG figures are measured in laboratory conditions and are typically 12–20% higher than real-world driving. We apply corrections automatically.
VCA dataset
Official UK fuel consumption data from the Vehicle Certification Agency. Most accurate.
CO2 formula
If no VCA data, we derive MPG from CO2 g/km emissions using the SMMT equivalence formula.
Engine size heuristic
For older vehicles without CO2 data, we estimate from engine capacity (cc).
40 MPG default
Used for very old or unusual vehicles with no other data available.
Real-world penalty applied: NEDC-tested figures (pre-2017) reduced by 20%. WLTP figures (post-2017) reduced by 12%. You can always override the MPG manually in step 2.
Data sources
UK Government Fuel Finder API
Live prices from all UK petrol stations, mandated by the CMA since 2024. Updated every hour. Covers 37,000+ stations.
View sourceDVLA VES API
Vehicle Enquiry Service — official DVLA lookup for make, fuel type, engine size, and CO2 by UK registration number.
View sourceVCA Fuel Consumption Dataset
Vehicle Certification Agency official dataset with tested fuel economy for thousands of UK-registered models.
View sourceBrowser Geolocation API
Your location is determined by your browser's built-in Geolocation API. We never store your coordinates.
Privacy & your data
Frequently Asked Questions
How does WorthThePump calculate fuel savings?
WorthThePump calculates your gross saving (price difference × fill amount), subtracts the extra fuel cost of the detour (round-trip miles ÷ your MPG × local price), and gives you a net saving in pounds. If the net saving is positive, the detour is worth it.
Where does WorthThePump get fuel prices?
Prices come from the UK Government Fuel Finder API, mandated by the Competition and Markets Authority (CMA) for all major UK fuel retailers. Prices are updated hourly and cover 37,000+ stations.
How is my car's MPG worked out?
We use a 4-layer approach: (1) Official MPG from the VCA dataset, (2) estimate from CO2 emissions using SMMT data, (3) engine size heuristic, (4) 40 MPG default. We then apply real-world penalties: NEDC figures are reduced by 20%, WLTP by 12%, to reflect actual driving conditions.
Is my vehicle registration stored?
No. For anonymous users, vehicle registration numbers are sent in the body of a POST request (not in the URL) and are never stored in our database. We cache vehicle specs (MPG, fuel type, engine size) for 24 hours by registration hash to avoid excessive DVLA API calls, but not the registration itself.
What vehicles does WorthThePump support?
WorthThePump supports all petrol and diesel vehicles registered in the UK, plus hybrid vehicles (which are resolved to their pump fuel type). Full electric vehicles (EVs) are not supported as they don't use pump fuel.
Ready to see your saving?
Enter your number plate and we'll tell you in seconds.
Try WorthThePump — it's free