UK fuel price trends: what affects pump prices?
What goes into the price of a litre, why it moves, and what that means for when you fill up.
Key points
- Tax is roughly half of every litre. Duty is fixed per litre; VAT is 20% on top.
- Oil prices and the pound move the rest, with a lag of a week or two.
- In September 2026, unleaded rose 5.3p and diesel 7.3p a litre across the same 7,400 stations.
What's in a litre
Wholesale fuel
The biggest moving part. Refined fuel is priced in US dollars on international markets, so both the oil price and the exchange rate feed through.
Fuel duty
A fixed amount per litre of petrol and diesel: 52.95p for much of 2026 (check GOV.UK for the current rate). It doesn't change with the oil price, so it's a bigger share of the price when oil is cheap.
VAT
20%, charged on the total including duty. On a 158.9p litre, VAT is about 26.5p.
Retailer margin
Covers delivery, staff, the site and profit. It varies most from station to station, and it's where comparing prices pays off. Supermarkets tend to run thin margins; motorway services and isolated rural sites run the widest.
What moves prices
- Crude oil. OPEC+ output decisions and geopolitical events can push prices up within a week or two.
- The pound. Fuel is bought in dollars. A weaker pound makes every litre dearer even if oil hasn't moved.
- Refining and supply. Diesel competes with heating oil and jet fuel for refinery output, so it can stay high in winter.
- "Rockets and feathers". Prices tend to rise quickly and fall slowly. Competitive areas pass cuts on faster.
How prices moved in September 2026
Comparing the same stations from 8 to 25 September 2026, Tanki's data shows a clear rise:
| Fuel | 8 Sept | 25 Sept | Change |
|---|---|---|---|
| Unleaded (E10) | 153.5p | 158.8p | +5.3p |
| Diesel (B7) | 183.9p | 191.2p | +7.3p |
Averages across around 7,400 stations reporting both days.
Seasons and days of the week
Demand rises in the summer driving season, and diesel can stay high through winter. These patterns are easily overridden by world events.
Any day-of-week pattern is small. On any given day, the spread between stations is far bigger: in late September 2026 the cheapest tenth of stations sold unleaded 13p a litre below the priciest tenth.
Supermarkets set the pace
The big supermarkets sell a large share of UK road fuel and price it keenly to bring in shoppers. Where several compete, prices fall for everyone nearby. See our supermarket fuel comparison.
Timing your fill-ups
- Compare before you fill. Station-to-station gaps beat any timing trick.
- Don't run near empty. A quarter of a tank gives you room to choose where you stop.
- When wholesale prices fall, give it a few days. Pump prices follow with a lag.
Tanki's Fill now or wait? card tracks your local prices over the last three weeks. Pro members get a verdict on whether prices near them are rising or falling.
Questions
How much of the pump price is tax?
Roughly half. Fuel duty is a fixed amount per litre and VAT at 20% is charged on top of everything, including the duty.
Why do prices rise faster than they fall?
Retailers pass on wholesale increases quickly but cut prices more slowly, especially where there's little local competition. Competitive areas pass savings on faster.
Is there a cheapest day to buy fuel?
Any day-of-week effect is small. The gap between stations on the same day is far bigger, so comparing prices matters more than timing.