Why is diesel dearer than petrol in the UK?

For years UK diesel and petrol carried the same fuel duty, yet diesel has usually cost more at the pump since the early 2020s. In autumn 2026 the gap is wide: the RAC recorded diesel at about 195p a litre on 21 September against about 172p for petrol, a difference of more than 20p.

Same duty, different cost of making it

Fuel duty is 52.95p a litre on both fuels, and VAT is 20% on the total. The difference therefore comes from the product itself. Europe makes less diesel than it burns and imports a lot of it, while it has a surplus of petrol. When imports are disrupted, diesel is hit first.

What changed in 2026

The conflict involving Iran from the end of February 2026 damaged refining capacity and disrupted shipping through the Strait of Hormuz. Diesel and jet fuel were the products most exposed, so wholesale diesel rose faster than wholesale petrol, and forecourts passed that on.

What diesel drivers can do

• Compare prices before you fill: the spread between forecourts in one town is often 5p a litre or more (see the cheapest stations).
• Avoid motorway services, where diesel is usually the most expensive.
• Check your cost per mile – a diesel car can still be cheaper to run per mile because it does more miles per gallon.

The live averages are at the top of this page and on the UK home page.

What is behind the gap?

Fuel duty is the same on both fuels, so the difference does not come from tax policy. It comes from the cost of the product before tax, and from what happens to that cost on its way to the forecourt.

• Global demand for diesel. Diesel is the fuel of lorries, vans, buses, trains, farm machinery and ships, as well as cars. When freight and industry are busy, or when a conflict disrupts supply of middle distillates (the group of products that includes diesel, heating oil and jet fuel), the wholesale price of diesel rises faster than petrol’s.
• Refinery mix. Crude oil is refined into a fixed range of products. European refineries were built around petrol, and the continent has for years imported diesel from the Middle East, India and the US. Any disruption to those flows pushes the import price up.
• VAT on a higher base. VAT is charged at 20% on the price including duty. A higher pre-tax cost for diesel is therefore magnified when the VAT is added.
• Retail margins. Forecourts tend to widen margins when wholesale prices are volatile, and diesel is the fuel where wholesale swings have been largest.

How to see the gap on today’s data

The live block at the top of this page shows the current UK average for both fuels. The simplest measure is the difference between the average diesel and unleaded (E10) price. When that difference is more than about 10p a litre, a diesel driver pays noticeably more for each mile, and it is worth checking the stations near you rather than assuming the cheapest option is the nearest.

What it means for diesel drivers

A diesel car usually does more miles per gallon than the petrol version of the same model, so the higher pump price is partly offset. As a rough rule, a diesel that does 10% better MPG breaks even on running cost when its fuel is about 10% dearer. Beyond that, the petrol car is cheaper to run per mile. Our cost per mile guide shows how to work it out for your own car.

Diesel drivers should also look at the other factors that do not appear at the pump: Clean Air Zone charges in some cities (see Clean Air Zones and fuel type), the higher purchase price of many diesel models, and the extra cost of servicing particulate filters if most journeys are short.

Will the gap close?

Nobody can forecast it reliably. Historically the diesel premium has narrowed when supply routes normalised and widened during winter, when heating-oil demand competes with road diesel. Following the weekly price changes on our trends page is a more useful guide than headlines.

Frequently asked questions