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1. Where the prices come from
Pump prices come from a public station feed covering the Netherlands, Belgium, Germany, Luxembourg and France. Each recommendation shows when Tankmapper fetched the prices. This is not the measurement time at the pump: the source provides no measurement time per station, so freshness is uncertain. Prices may change before you arrive. Implausible prices are filtered out; missing prices are shown as unknown rather than estimated.
2. How we filter bad readings
Crowd-sourced and scraped price data contains mistakes: a missing decimal, a promotional price for a different grade, a station that has closed. Two rules run before any calculation:
- Any reading outside €0.40–€4.50 per litre is discarded; nothing in Western Europe is plausibly outside that band.
- A reading more than 35% below the median for that country and fuel grade is discarded, provided we have at least five stations to compare against. This removes the “too good to be true” outliers that would otherwise dominate the advice.
3. Distance and detour
The cheapest pump is worthless if it is 20 kilometres off your route. We first shortlist candidates near the route with a fast straight-line filter, then request real driving distances and durations for start → station and station → destination from an OpenStreetMap-based routing engine. The detour is the difference between that and your direct route. Candidates beyond your maximum acceptable detour are removed entirely.
4. Tank, reserve and partial fills
From your tank size, current level (via the fuel-gauge slider or an estimated range) and your consumption, we compute how far you can still drive. We keep a reserve buffer rather than planning you down to the last drop. On longer trips we plan several stops, and for each one we compute how many litres actually fit and how many you need to reach the next stop or your destination. That is why the advice sometimes says “partial fill”: buying 30 litres at a cheap station can beat filling up at an expensive one.
5. What the savings figure means
A saving only means something against a named baseline. Ours is: the first suitable station you would realistically reach on your route without planning. The net saving subtracts the fuel burnt on the detour itself. Extra travel time is reported separately, in minutes, and never converted into money — what your time is worth is your call, not ours.
6. Opening hours and fuel availability
Opening hours, brand and which grades a station sells come from OpenStreetMap, alongside the price feed. That data is volunteer-maintained and incomplete. Where we have it, we show it with its source; where we do not, we say it is unknown instead of guessing.
7. Known limitations
- Prices can change between retrieval and your arrival; the measurement time is unknown.
- Unmanned and supermarket stations are not equally well covered in every country.
- Consumption is an average; towing, headwind, load and speed all move it.
- Licence-plate lookup is available for Dutch plates; for BE, DE and FR you pick your make and model.
Spotted a wrong price or a station that no longer exists? Mail us at info@tankmapper.nl — corrections make the advice better for everyone. See also our frequently asked questions.
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