E.S. Sobrosa-Paredes

Same logic: pick plain diesel in the selector and open your municipality. The gap between the cheapest and the most expensive station in one district often reaches ten cents a litre, which on a 50-litre tank is five euros on the same trip.

Fuels obtained from oil, natural gas and coal, formed over millions of years from organic matter. The petrol, diesel, LPG and compressed natural gas sold at stations are all of fossil origin. Burning them releases the carbon that was locked away, which is where their climate footprint comes from.

Liquid fuels made in a plant rather than refined from crude oil. They combine hydrogen, obtained by splitting water, with carbon dioxide captured from the air or from industry. The result is chemically close to petrol or diesel and runs in today's engines unchanged. They are not sold at Portuguese stations yet: production is expensive and it takes a great deal of energy.

Because most operators adjust their grid at the start of the commercial week, based on the previous week's international quotations and the EUR/USD rate. It is market practice rather than a rule, which is why some stations move on other days.

The price is set station by station, not by the brand. Location, the competition a few kilometres away, sales volume and the cost of hauling fuel to the tank all weigh in. That is why comparing within a single municipality is worth doing.

No. The figure shown is the retail price reported by the station. Loyalty, supermarket and fleet card discounts are applied afterwards, at the pump or on the invoice, and vary from campaign to campaign.

From DGEG, the Directorate-General for Energy and Geology. Since 2008 every station in mainland Portugal has been required to report its price before charging it. The autonomous regions run their own regimes, with regulated maximum prices, and have separate pages.