Start with the quantity, not the headline difference
A lower price per litre is only one part of a useful refuelling decision. The possible saving depends on how much you buy, while reaching the station uses fuel and time. Compare the additional journey with the stop you would otherwise make, including any extra drive back to your route.
For liquid fuel sold by the litre, calculate:
Gross saving = litres bought × price difference in euros per litre.
Extra fuel cost = extra kilometres × consumption in litres per 100 km ÷ 100 × assumed fuel cost per litre.
Use compatible units. For CNG bought by the kilogram, the first calculation uses kilograms and euros per kilogram; consumption must also be expressed in suitable units for the second.
A hypothetical example
Assume you need 35 litres of petrol, a farther station is €0.08/litre cheaper, and choosing it adds 8 km compared with your alternative stop. Assume consumption of 6.5 litres/100 km and value the extra fuel at €1.80/litre.
- Gross saving: 35 × €0.08 = €2.80.
- Extra fuel: 8 × 6.5 ÷ 100 = 0.52 litres.
- Extra fuel cost: 0.52 × €1.80 = €0.94, rounded.
- Difference after extra fuel: approximately €1.86.
These assumptions illustrate the arithmetic; they are not current station prices or a forecast. The result excludes any toll difference and the value of your time. Stop-start traffic, a different consumption rate or a smaller fill can change it.
Use PienoGo to compare the practical choices
- Search near your location and choose your fuel. Match self (self-service) or servito (attended service) when comparing prices.
- Open Refuel, choose your vehicle or fuel and optionally enter an amount. Compare its Balanced, Price and Time preferences according to your priorities.
- For a planned journey, use Plan a trip and compare stations’ extra distance and time. Treat unverified detours as approximate.
- Read the station’s price details and last update before opening Directions.
Smart Trip can add traffic-aware checks within your account’s monthly allowance. Its extra driving time excludes queues and refuelling. Reported MIMIT prices are useful inputs, but an estimated saving is not a guaranteed amount at the pump.
Common questions
How do I value my time?
There is no single correct rate. Decide whether the remaining saving justifies the extra minutes in your situation, including filling, paying and possible waiting.
Should I use distance from my current location?
Use the additional distance caused by choosing the cheaper stop. If both options require driving, comparing their complete journeys avoids charging only one option for travel.
What if I already pass the cheaper station?
Its additional driving cost may be small. Still compare access, the required service type and the freshness of the reported price.