What happened
Oil prices fell on Tuesday 10 November after the US president said the war on Iran was "effectively over". As Julia Kollewe reported for the Guardian, Brent crude, the global benchmark, dropped nearly 3% to $89.66 a barrel on Tuesday morning, the lowest since 31 August, after a fall of almost 6% on Monday.
The Department for Energy Security and Net Zero's weekly road fuel prices, published at 9:30 the same morning, show how little of that has reached the forecourt so far. The UK average for the week of 9 November was 198.19p a litre for diesel and 170.71p for petrol. Diesel is down only 1.8p from the record 200.04p of the week of 12 October.
Pump prices have not caught up
The last time Brent was this low, at the end of August, the same DESNZ series looked like this:
| UK average pump price | Week of 31 August | Week of 9 November | Difference |
|---|---|---|---|
| Diesel | 183.49p | 198.19p | +14.7p |
| Petrol | 161.61p | 170.71p | +9.1p |
Fuel duty was 52.95p a litre and VAT 20% in both weeks, so tax isn't the reason. Pump prices follow wholesale fuel with a lag, and diesel carries the refining premium we covered when Shell and bp reported their third quarter. A falling crude price doesn't guarantee pump prices will follow quickly or all the way.
What it means for your business
An illustrative firm whose vans burn 5,000 litres of diesel a month pays £9,910 at this week's average, against £9,175 at the end of August: £735 a month more for exactly the same driving. Its emissions are the same in both months: 12.92 tonnes CO2e, at 2.58354 kg CO2e a litre under the 2026 government factors.
A footprint worked out from pounds spent tells a different story. Using Defra's spend factor for "Coke and refined petroleum products" (1.04558 kg CO2e per £ excluding VAT, 2023 figures), the same 5,000 litres come out at 8.63 tonnes this week and 7.99 tonnes at August prices. If pump prices now fall back, a spend-based estimate will show a cut of about 7.4% that the fleet never made. We explained the same problem in reverse when diesel hit 200p in October.
The wider picture: the Global Carbon Budget published today expects fossil CO2 emissions to dip in 2026, helped by a drop in oil use after the Iran conflict. Cheaper oil could work the other way, which is one more reason to judge your own progress on litres and miles.
What to do now
- Keep counting litres. Ask your fuel card provider for a transaction report with litres and fuel type for each fill-up, and keep till receipts for fuel bought on cards or expenses.
- Watch Tuesday's figures before fixing a budget. DESNZ publishes the UK average each Tuesday morning; our petrol and diesel price tool charts the series.
- Check your fuel card price. If your fuel card has a fixed weekly price, ask your provider how and when a lower crude price feeds into it.
- Don't read a cheaper month as a carbon cut. If your figures come from your ledger, take fuel accounts out of any spend-based estimate and enter the litres instead. Our post on spend-based Scope 3 explains what to leave out.
