If you're hiring a car in Portugal, check which fuel it takes before you do. From tomorrow, regular 95-octane petrol is forecast to drop by about 2.5 cents a litre to roughly €2.031, while regular diesel is heading the other way — up 2 cents to around €2.192. Those figures come from forecasts by the National Association of Fuel Retailers (Anarec), working from the latest data published by the country's energy directorate, DGEG, and they already account for the scheduled adjustment to Portugal's tax on petroleum and energy products (ISP).

It's a modest but noticeable divergence at the pump, and for anyone planning a road trip down the Alentejo coast or through the Douro Valley, diesel drivers will simply pay more per tank than they did last week. At over €2.19 a litre, diesel in Portugal now sits well above many UK and German prices, so filling up strategically matters on longer routes.

The reason prices are moving at all is bigger than Portugal. Brent crude for December delivery has climbed to $117 a barrel, up from around $114 the week before. Behind that sit the war involving Iran, wider Middle East tensions and the effective closure of the Strait of Hormuz — the chokepoint that handles roughly 20% of global oil and natural gas trade. Attacks on refineries linked to the war in Ukraine have added further pressure. In short, there's no quick relief in sight, and travellers should expect fuel costs to stay volatile rather than settle.

Practically, the takeaway for a self-drive holiday in Portugal is straightforward: budget realistically for fuel, and if you have a choice of hire car, a petrol model is now the cheaper bet per litre. Petrol at about €2.03 versus diesel at €2.19 is a difference of roughly €14 on a 100-litre comparison — or more relevantly, a few euros per fill-up on a typical week's driving. Apps that track live pump prices are widely used in Portugal, and prices can vary a little between motorway services and town stations, so it pays to compare before you commit.

This is worth watching if you're booking a Portuguese road trip in the coming months: fuel is one of the few holiday costs that can change overnight, and with the Middle East situation unresolved, the trend line points up rather than down. Petrol drivers get a small break tomorrow; everyone else should build a fuel buffer into the budget.

Reported by Portugal Resident.