Why the price of diesel is rising more than that of petrol

Context & Explainers

The ISP is Portugal's excise tax on fuels — the Tax on Petroleum and Energy Products (Imposto sobre Produtos Petrolíferos e Energéticos) — charged as a unit rate per litre on petrol, diesel and other fuels. The government sets and can temporarily cut those unit rates; a recent decision to reduce the rate for road diesel on the mainland aims to lower pump prices and reduce transport costs for drivers and businesses, though it also lowers tax revenue.

Higher crude oil prices raise wholesale fuel costs, and those increases typically reach Portuguese petrol and diesel pumps within days to weeks; the recent conflict has pushed oil to one‑year highs and European gas futures up roughly 40%, making fuel the first likely victim. Final pump prices also depend on taxes, VAT and distributor margins, so consumers should expect higher filling‑station bills but the exact change will reflect those tax and margin components as well as exchange rates.