How Hormuz disruption reaches your pump price

On Jul 5, Iranian forces turned six merchant ships out of the Omani corridor and back into Iran-designated lanes. Transit times rose about four hours. No cargo was damaged, no vessel was detained, and no barrel failed to arrive. The most common question the desk received the following morning was whether that would show up at the pump — and if so, when.

The short answer is that a four-hour delay, on its own, does not. The longer answer is more useful: a crude price move caused by events at Hormuz reaches a retail forecourt through five separate pricing steps, each with its own lag, its own margin, and its own local distortions. By the time it arrives it has been diluted by tax, buffered by inventory, and stretched across weeks.

This piece walks the chain link by link, with the arithmetic at each step. Every figure here is illustrative sample data drawn from published price series and desk estimates — the point is the structure of the transmission, not a forecast of any particular week's number.

The chain link by link

1. A headline moves the crude benchmark. Brent and Dubai futures reprice within minutes on risk to Hormuz volumes, whether or not a barrel is actually lost.
2. Refined product futures follow. Gasoil, diesel and gasoline contracts move in the same session, but rarely by the same proportion — the gap between them is the crack spread.
3. Refiners reset their offer. The crack spread determines how much of the crude move a refinery passes on versus absorbs, and it is driven as much by maintenance and product inventories as by crude.
4. Wholesale rack prices adjust at the terminal. This is the price a fuel retailer actually pays for the next truckload, and it tracks product futures with a lag of roughly one to five days.
5. The retail sign changes. Stations reprice against replacement cost, tank turnover, and whatever the competitor across the road is charging — the slowest and most local link in the chain.

That figure is the ceiling, not the expectation. A $10 a barrel crude move is worth roughly 24 US cents a gallon — about 6.3 cents a litre — if every cent were passed through immediately and in full. In practice the pass-through is partial in the short run and closer to complete only after several weeks.

Where the benchmark price moves

Crude benchmarks price expectation, not delivery. Through the Feb 28 escalation and the Jun 12–20 breakdown over mine clearing, the benchmark response tracked perceived closure risk rather than measured transit volumes — prices moved on the day of announcements, not on the days transits actually fell.

This matters for reading the current period. The interim memorandum signed in Muscat on Jun 24 opened a 60-day fee-free window; it did not restore pre-crisis volumes. Benchmarks have carried a risk premium against the possibility that the window lapses, which is a different thing from pricing a physical shortfall.

The refinery margin step

A refinery buys crude and sells products. The difference, per barrel, is the crack spread — and it is the single most misread link in the chain. When crude rises and the crack narrows, the refiner is absorbing part of the move and the pump lags. When crude is flat and the crack widens — typically because of an outage, a maintenance season, or a run on diesel — pump prices can rise with no crude story behind them at all.

Hormuz disruption tends to hit the crack spread on both sides. It raises the crude input cost for refiners everywhere, and it disproportionately threatens the medium and heavy sour grades that Gulf producers ship — which are the feedstock for diesel and jet. That is why diesel typically moves further and faster than gasoline in a Hormuz event, and why a driver of a diesel vehicle sees the shock earlier than a petrol driver in the same town.

Wholesale rack and the delivery lag

The rack price is where the abstract becomes concrete. It is the posted price at a distribution terminal for a truckload of product, reset daily, and it is what an independent station operator actually pays. Rack prices track product futures closely but not instantly, because terminals price against the replacement cost of inventory they already hold.

A station with a 30,000-litre tank selling 4,000 litres a day is turning its stock roughly every week. Until that tank is refilled at the new rack price, the operator's cost base has not actually changed — which is the mechanical part of the lag. The behavioural part comes next.

Tax is the biggest single line

In most of Europe, more of what a driver pays is tax than is crude. This is the reason the same $10 a barrel move produces very different pump responses in different countries: excise duty is a fixed amount per litre and does not move with crude at all, so it acts as a shock absorber. Value-added tax, charged as a percentage, does amplify the move — but only on the smaller pre-tax base.

Rockets and feathers

Retail fuel prices are widely observed to rise faster than they fall — up like a rocket, down like a feather. The asymmetry has been documented across dozens of national markets since the early 1990s, and the size of it is consistent: a rise in wholesale cost typically reaches the pump in about half the time a fall of the same size does.

The strait sets the direction of the move. Local market structure sets how fast it arrives and how slowly it leaves.

straitofhormuzs.com desk note, Jul 6, 2026

The mechanism is competitive rather than conspiratorial. When costs rise, every operator has the same incentive and the same justification to move at once. When costs fall, an operator who holds the old price earns margin until a competitor undercuts — and in a market with few competitors, that can take weeks. The practical consequence for a driver following a Hormuz story is that the upside is visible within a fortnight and the relief, if the story resolves, takes about twice as long.

How to read your own market

You do not need a terminal subscription to work out whether a local price move is a Hormuz move. The following checks separate the transmitted signal from local noise.

• Compare diesel with petrol. A Hormuz-driven move usually hits diesel harder, because Gulf sour crude is the feedstock most exposed and diesel cracks respond first.
• Check whether the wholesale benchmark for your region moved before your station did. If it did not, the cause is local — a supply outage, a terminal issue, or a competitor closing.
• Look at three stations on different supply contracts, not one. A single brand's repricing schedule tells you about that brand, not about the market.
• Strip out the tax line before comparing across borders. A 5% rise in Germany and a 5% rise in the United States are not the same event in pre-tax terms.
• Note the date the price changed, not the date you noticed. Retail lag is measured from the wholesale move, and reconstructing it after the fact requires the actual dates.
• Treat freight and war-risk insurance as separate inputs. In a partially restricted strait they can move independently of the crude benchmark and still reach the rack.

1. Take the crude move in dollars per barrel and divide by 42 to get the arithmetic effect in dollars per US gallon, or divide by 159 for dollars per litre.
2. Multiply by the pass-through you expect over your horizon — roughly half within two weeks, most of the rest by week eight in a competitive market.
3. Multiply by your market's pre-tax share from the table above to account for the fixed duty wedge.
4. Add your local percentage sales tax or VAT on top of the result, not on the crude figure.
5. Compare the answer with what the sign actually says. A persistent gap in either direction is a local margin story worth investigating.

What would break this pattern

Everything above describes transmission during a disruption that raises cost and delay without removing volume. The current interim arrangement — day 14 of a 60-day fee-free window, with Iran retaining routing designation — sits in that category. Three developments would change the mechanics rather than the magnitude.

• An actual volume shortfall rather than a delay. If transits fall far enough that refiners cannot source replacement barrels of similar grade, the crack spread stops absorbing the shock and starts amplifying it, and the retail lag compresses sharply.
• A physical incident in a designated lane. The Jul 1 grounding near Larak Island did not close either lane. One that did would price insurance and freight before it priced crude.
• Government intervention in the tax line. Duty cuts, price caps and subsidy changes break the arithmetic entirely — in several markets they have historically arrived faster than the underlying crude move reached the pump.

Until one of those three things happens, the honest framing for a driver is this: what the strait is doing today shows up on the forecourt sign in about two weeks, at roughly half strength, diluted by whatever share of the price your government already takes. Treat every number on this page as illustrative sample data and check it against your own local wholesale series before drawing conclusions.