President Trump says the war in Iran will be over soon, bringing quick relief to Americans facing average gas prices that are now more than $0.64 higher than this time last month. But history suggests that any eventual return to normalcy at gas pumps is likely to be a drawn-out process.

Previous presidents, most recently Joe Biden, know the pattern well.

As the Federal Reserve Bank of St. Louis explained in 2022, crude oil and refined gas prices don't always move in tandem, a phenomenon known as "rockets and feathers."

They often shoot upward together (like a rocket), but when crude oil prices later fall, gasoline prices sometimes drift down at a much slower rate (like a feather).

The concept has already been in limited evidence in recent days.

The rocket side of the equation was clear last week when hostilities began and the price of crude oil — both international benchmark Brent crude (BZ=F) and US benchmark West Texas Intermediate (CL=F) — shot up. Pump prices went up quickly with them.

But on Monday and Tuesday, crude oil prices fell 25% from a late Sunday peak — a change that hasn't yet been reflected at the pumps.

In fact, average pump prices have moved up in that time period, according to the American Automobile Association (AAA). The average cost per gallon was $3.47 on Monday, $3.53 on Tuesday, and is now $3.57 on Wednesday, according to the group.

That hasn't changed the White House narrative. Press secretary Karoline Leavitt told reporters on Tuesday that when hostilities end, "Americans will see oil and gas prices drop rapidly, potentially even lower than they were prior to the start of the operation."

Read more: What an extended war with Iran could mean for gas prices

The formal economic term for the phenomenon is "asymmetric pass-through" and stems from a variety of causes, including the lag between refiners buying crude oil and then selling their refined product and the need to preemptively protect bottom lines in moments of uncertainty.

What it means in practice is that drivers are often the last to feel relief when oil shocks ease. That also means outsized political costs with voters angry about the lingering price increases, which flared during the Biden administration.

It was in the aftermath of Vladimir Putin's invasion of Ukraine in 2022 that both crude oil and pump prices spiked. Prices at the pump then stayed elevated even after crude oil prices eased, frustrating Biden and his aides for months.

In a March 16 briefing that year, then-Press Secretary Jen Psaki said, "many accept that gas prices rise quickly but fall slowly — the so-called 'rockets-and-feathers' phenomenon — but President Biden rejects that."

She added there was "no excuse for excessive price increases, profit padding, or any effort to exploit American consumers."

The pressure campaign had little effect, and Biden was still focused on the issue months later in July, tweeting an appeal to stations to "bring down the price you are charging at the pump."

Another bout of price asymmetry isn't a certainty in 2026 — the St. Louis Fed noted that this phenomenon doesn't occur every time — but it could easily haunt Trump if pump prices are slow to fall.

The current dynamics have led Patrick De Haan, GasBuddy's head of petroleum analysis, to forecast that recent crude oil drops are likely for now to "stall out" more increases at the pump and that some limited price relief could be in the offing — but that sustained price relief may not be felt for a while.

Larger drops in oil prices could be further delayed by the uncertain end to hostilities and a bottleneck that is likely to remain in the crude oil markets even if the conflict de-escalates quickly.

Trump said on Monday he is looking to end the air campaign, but that it won't be done this week. Defense Secretary Pete Hegseth then announced that Tuesday "will be our most intense day of strikes."

Energy market jitters remained elevated after CNN reported late Tuesday that Iran appears to be laying mines in the Strait of Hormuz, and then three vessels were reportedly hit by suspected projectiles in the region on Wednesday.

The bottom line for overall energy prices, as oil market researcher and founder of CommodityContext.com Rory Johnston put it, is that "even if the conflict ended today and tankers ramped back up to 100% Hormuz flow, it would still take months to return to anything resembling normality."

The White House, for now, isn’t providing more detail on how it plans to ensure that gas prices fall rapidly after hostilities end.

White House spokesperson Taylor Rogers responded to questions from Yahoo Finance about whether the White House would pressure gas station operators to lower prices with a statement reading in part, "President Trump has been clear that these are short-term disruptions."

She reiterated the promise that prices would drop rapidly and "as a result, American families will benefit greatly in the long-term."

Ben Werschkul is a Washington correspondent for Yahoo Finance.

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