1. The short answer
Petrol averaged 164.4 pence a litre and diesel 186.4 pence in the week to 7 September 2026, and both figures are already a week or more old by the time you read this because the pump follows Brent and wholesale margins with a lag. No one, including us, can hand you a reliable pence-per-litre number for next month. What can be shown is the structure: Fuel Duty plus VAT together make up roughly half the pump price, fixed by policy and unaffected by the oil market until at least 31 December 2026, and the rest tracks crude and the diesel crack spread, both of which have moved sharply in September.
That structure is why this page gives scenarios rather than a forecast. Crude at $103.98 a barrel on 11 September was up about 9 percent on the week amid disruption to two Middle East shipping routes. Whether that holds, eases or worsens changes the floating half of your pump price, but not the fixed half.
2. What is actually in a litre: duty, VAT and the rest
Short answer: Fuel Duty and VAT together make up roughly half the pump price, and that share is fixed by policy through the end of 2026. Fuel Duty is charged at 52.95 pence per litre on both petrol and diesel, a rate that has applied unchanged since March 2022 and is held at that level until 31 December 2026 under the government's temporary duty cut extension. VAT at 20 percent is then applied on top of the pump price, including the duty already added, so the tax is levied on tax.
The arithmetic on the 164.4 pence petrol average: VAT is 20 percent of the whole pump price, so it works out to 164.4 x 20 / 120 = 27.40 pence. Add the 52.95 pence duty and tax totals 80.35 pence, or 48.9 percent of the pump price. On the 186.4 pence diesel average, VAT is 31.07 pence, so duty plus VAT is 84.02 pence, or 45.1 percent. The remainder, crude, refining and distribution margin, and retailer margin, is the part that moves week to week with the oil market. It is worth remembering this when a headline says "petrol prices surge": the tax floor does not move, so the whole visible swing sits in the smaller, floating share.
After 31 December 2026, the government's own schedule shows Fuel Duty rising on 1 January 2027 and again on 1 March 2027, moving back toward pre-2022 levels. That is a policy date, not a market one, and it applies regardless of what crude does.
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3. Why diesel costs more than petrol: crude, the crack spread and the diesel premium
Short answer: diesel averaged 22.0 pence a litre more than petrol in the same week, and that gap sits almost entirely in the refining margin, not in tax. Fuel Duty is identical for both fuels at 52.95 pence per litre, so the 22.0 pence difference between 186.4 and 164.4 pence comes from what refiners charge to turn crude into diesel versus petrol, a margin known as the crack spread. Our diesel crack spread explainer covers how that margin is calculated and why it tends to widen when distillate stocks are tight, as they were globally through early September 2026.
Brent crude itself closed at $103.98 a barrel (Trading Economics closing indication) on 11 September 2026, having traded above $100 all week and touched a weekly high of $107.60, a roughly 9 percent weekly rise driven by disruption around two Middle East shipping chokepoints. Because UK pump prices are priced in sterling off a dollar-denominated crude and product market, the pound to dollar exchange rate also affects the wholesale cost base, though we do not have a verified rate for this specific week to quote here.
4. Three scenarios for the months ahead, not a forecast
Because the crude and refining side of the price depends on events that cannot be predicted with confidence, this page sets out scenarios rather than a single number. Treat all three as illustrative directions, not targets.
| Scenario | What would have to happen | Likely direction for UK pump prices |
|---|---|---|
| Hormuz reopening | A verified, sustained increase in tanker transits through the Strait of Hormuz and an easing of Red Sea shipping disruption | Downward pressure on Brent and on the diesel crack spread, working through to pump prices with the usual multi-week lag |
| Status quo | Shipping constraints persist at current levels, distillate stocks stay tight, Fuel Duty and VAT unchanged | Pump prices track crude and the crack spread sideways to firmer, broadly in line with the pattern seen since late August |
| Escalation | Further disruption to Gulf or Red Sea shipping routes, additional supply outages | Upward pressure on crude and diesel margins, with diesel likely to widen further against petrol given tighter distillate stocks |
None of these is a prediction of what will happen, only of what each path would mean for the price if it did. The fixed tax component stays the same in all three scenarios until at least 31 December 2026, which is the one part of the pump price you can rely on for planning.
See how a change in crude oil would work through to a household budget.
Run the scenario5. How UK pricing compares with the wider energy cost picture
Petrol and diesel are only part of a UK household's energy exposure this winter. Domestic gas and electricity bills are set separately, under the Ofgem price cap; our Ofgem price cap forecast and energy price cap for October 2026 pages cover that side in detail. Households that heat with kerosene rather than mains gas, common in off-grid areas, face a different price mechanism again, covered on our UK heating oil and kerosene prices page.
What links all of these is the same crude and wholesale market described above: a tighter distillate market pushes up diesel and heating oil together, since they are close relatives in the refining process, while petrol and gas follow a looser relationship to crude.
6. What you can control while the market is volatile
You cannot influence Fuel Duty, VAT or the crude price, but fuel consumption itself responds to driving style and vehicle upkeep, and those savings apply whatever direction pump prices go next. Our mobility savings tips cover a full range of options, including checking tyre pressure, since under-inflated tyres increase rolling resistance and fuel use, and adopting smoother acceleration and earlier gear changes to cut consumption per mile.
None of these tips offset a genuine supply shock, but they are the only lever on this page that is fully within a driver's control, unlike duty policy or the Brent price.