The number that every retailer has been dreading finally arrived.

On Tuesday, the national average price of regular gasoline crossed $4.02 per gallon, according to AAA — the first time it's been above $4 since the summer of 2022. Diesel, the fuel that powers the trucks, trains, and ships that move virtually every product on a retail shelf, is even worse: $5.45 per gallon, up from about $3.76 before the Iran conflict began in late February.

As we've reported throughout March, the Strait of Hormuz crisis has been reshaping global shipping routes and energy markets since the joint U.S.-Israeli strikes on Iran on February 28. But $4 gas isn't just a geopolitical headline anymore. It's a line item on every retailer's P&L — and a psychological threshold for consumers that historically triggers real behavior change.

The Retailer Math

The diesel surge is the more urgent number for the industry. Transportation costs account for roughly 5-8% of total retail operating expenses on average, and diesel is the single largest variable within that bucket. A 45% increase in diesel prices — which is approximately what's happened since February — translates to meaningful margin pressure across every category.

Grocers feel it first. Fresh food supply chains are fuel-intensive by nature — refrigerated trucks burn more diesel than dry freight, and the just-in-time replenishment model that grocers depend on means there's no inventory buffer to smooth out cost spikes. Analysts at J.P. Morgan have warned that grocery prices could see additional hikes by mid-April as transportation and packaging cost increases flow through to the shelf.

Apparel-heavy retailers like Gap, Carter's, and Kontoor Brands, already squeezed by tariff-related margin pressure, face a compounding problem: their supply chains run through Asia, and the rerouting of container ships away from the Strait of Hormuz is adding both transit time and fuel surcharges to already elevated logistics costs.

The Consumer Psychology

But the bigger retail story may be what happens in the consumer's head when they see $4 on the gas station sign.

A recent AP-NORC poll found that 45% of U.S. adults are "extremely or very concerned" about being able to afford gas in the next few months. That kind of anxiety doesn't stay at the pump. It follows shoppers into the store, into the app, into every discretionary purchase decision.

CNN's analysis put it bluntly: Americans are spending hundreds of millions of dollars more on gasoline every day than they were two months ago. That money comes from somewhere — and for most households, it comes from the discretionary budget that retailers depend on.

The historical playbook is clear. When gas prices spike, consumers trade down: they shift from branded to private label, from department stores to dollar stores, from dining out to eating in. The last time gas was consistently above $4, in mid-2022, Walmart and Dollar General reported surges in new customers from higher-income brackets seeking value.

What Comes Next

The uncomfortable truth for retail executives is that nobody knows when — or if — this resolves. Oil prices are being driven by a geopolitical conflict with no visible off-ramp. Brent crude hit $126 per barrel at its peak in March and remains well above $100.

Retailers who haven't already locked in fuel surcharge caps with their 3PL partners are now negotiating from a position of weakness. Those who built fuel cost assumptions into Q1 guidance based on $3-a-gallon gas are looking at earnings revisions. And those selling to the lower-income consumer — which is most of American retail — are watching their customer's wallet get thinner by the week.

February's retail sales rebound, released today by the Census Bureau, painted a picture of a consumer still willing to spend. But that data was collected before $4 gas became reality. The April and May numbers will tell a very different story.