Crude fell back. UK petrol prices kept rising.
Brent rose twelve percent on 23 July and was below its starting point by the 27th. American pump prices rose, then eased. British pump prices rose, and kept going. Same barrel, same week, two different bills.
Our earlier report on the Strait of Hormuz attacks documented the chain from a projectile off Oman to the world crude price and then stopped, because we held no retail fuel data. We have it now, for two countries, on matching weeks.
What crude did
Brent spot, in dollars a barrel: 93.85 on 21 July, 94.12 on the 22nd, 105.32 on the 23rd, 100.31 on the 24th, and 91.82 on the 27th. Up about twelve percent in a day, then below where it started four days later.
What the pumps did
| Week commencing | US regular, $ per gallon | UK petrol, pence per litre |
|---|---|---|
| 20 July 2026 | 4.001 | 152.29 |
| 27 July 2026 | 4.096 | 156.13 |
| 3 August 2026 | 4.079 | 159.89 |
| Change over the fortnight | +1.9% | +5.0% |
Measured Both series include all taxes. US figures are EIA weekly retail, all formulations, released 4 August 2026. UK figures are DESNZ ultra-low sulphur unleaded petrol, published 4 August 2026. Percentages are our arithmetic on those published figures.
Both rose in the week that contained the twelve percent crude move. Then they parted. The American series turned down by 3 August. The British series added another 3.76 pence.
Diesel went further in both places, and much further in Britain. US on-highway diesel moved from $5.134 to $5.348 across the fortnight, up 4.2 percent. UK diesel moved from 167.08 pence to 179.19 pence, up 7.2 percent.
The tax arithmetic points the wrong way
UK fuel duty is a flat 52.95 pence a litre on both petrol and diesel, with VAT at 20 percent charged on top of the fuel-plus-duty total. On the 3 August petrol price of 159.89 pence, that works out at 52.95 pence of duty and 26.65 pence of VAT, so 79.60 pence of every litre, just under half, is tax.
The EIA publishes the American equivalent. In May 2026, a gallon of US regular gasoline at $4.48 was 52 percent crude oil, 22 percent refining, 15 percent distribution and marketing, and 12 percent taxes.
Measured Duty and VAT rates from the DESNZ weekly table. US composition from the EIA Gasoline and Diesel Fuel Update, May 2026. The pence split is our arithmetic on the published rates.
A large fixed tax component dilutes a crude move, because the fixed part cannot move. Just under half of a British litre is a number that does not respond to Brent at all. Twelve percent of an American gallon is. On that arithmetic alone, the steadier of the two prices was the British one.
It was the opposite. Over the same fortnight, with roughly half its pump price frozen by duty and VAT, the British petrol price rose two and a half times as much as the American one. On diesel it rose nearly twice as much. The component that could not move was the larger share, and the total moved further anyway.
What we cannot tell you
This section explains a mechanism. It contains no measurement.
Brent is quoted in US dollars and British pumps charge in pounds, so the sterling cost of a barrel depends on the exchange rate as well as the barrel. Refining margins, product specifications, retail competition, stock cycles and the timing of pass-through all differ between the two markets. Any of those could account for the gap.
We have measured none of them. We hold no exchange rate series, no refining margin data, and no wholesale price series for either country. The divergence in the table is a fact. The reason for it is not something we can source, and we are not going to guess at it in print.
Canada publishes monthly. This event lasted two weeks.
We promised Canadian figures and we do not have them in this piece. Statistics Canada publishes average retail gasoline prices monthly, and a monthly average cannot resolve a price event that began and ended inside two weeks. A source can be authoritative and still be the wrong instrument for the question.
Verifying a Canadian weekly series is the next piece of source work. Until that is done, this comparison runs on two countries.
What this changes about the Hormuz story
That article said the chain was documented from the strait to the world price and no further. It now runs one link further, and the link is not uniform. A twelve percent rise in crude that had fully unwound within four days still left British drivers paying five percent more a fortnight later, while American drivers were paying roughly two percent more and falling.
Whether that gap closes, and how fast, is the question the next set of weekly releases answers. Both agencies publish again on 11 August.
Sources and verification
Addresses below are printed in full so you can copy one and check us. We do not link out.
US retail prices and price composition. US Energy Information Administration, Gasoline and Diesel Fuel Update, released 4 August 2026. US federal work, public domain. Measured https://www.eia.gov/petroleum/gasdiesel/
UK retail prices, duty and VAT rates. UK Department for Energy Security and Net Zero, Weekly road fuel prices, week commencing 3 August 2026, published 4 August 2026. Accredited Official Statistics, Open Government Licence v3.0. Measured https://www.gov.uk/government/statistics/weekly-road-fuel-prices
Crude price. US Energy Information Administration Brent spot series, newest observation 27 July 2026. Measured
All percentages and the pence split are our own arithmetic on the published figures above, and can be reproduced from them.
Not measured here. Exchange rates, refining margins, wholesale prices, retail competition, and any Canadian figure at weekly resolution.