American fuel makers dialed down production this month, a move that will reduce gas supplies and threatens to slow the decline in gasoline prices.

Since hitting a record national average of $5 a gallon this summer, gasoline prices have tumbled about 91 cents and could slip to or below about $4 a gallon by mid-August, analysts said, as economic fears weigh on oil markets and American drivers cut back on fuel purchases.  

The longevity of the price reprieve depends partly on how much fuel refineries can continue to make, analysts said. Marathon Petroleum Corp. and Phillips 66, two of the biggest U.S. refiners, said they are planning maintenance work in the second half of the year, with others expected to slow operations during the fall after running at breakneck speed during the summer months.

“We really wanted to meet market demand,” said Raymond Brooks, an executive vice president at Marathon, in a call with investors this week. He was referring to the company’s refineries being maxed out in the second quarter. As a result, the refiner has to conduct $400 million in maintenance in the coming months, he said. 

Overall, U.S. oil refiners used 91% of their total fuel-making capacity last week, down from an annual high of 95% in late June and the lowest level since May, according to the Energy Information Administration. It is rare to see a 4-percentage-point drop in refinery runs during the summer, said Robert Yawger, executive director for energy futures at Mizuho Securities USA. 

“They were squeezing more blood out of a turnip than ever before,” Phil Flynn, a senior analyst at the Price Futures Group in Chicago, said of refiners. A slowdown by several refineries would contribute to bringing gasoline’s rapid descent to a stopping point, he said.

If the U.S. economy does go into recession, as many economists say it might, fuel demand and gas prices might fall further. But many of the factors that limited supplies and spurred record gasoline prices this summer will remain, including a dearth of fuel-making facilities. Another potential obstacle is the Atlantic hurricane season, when refineries often go offline if they fall in the path of severe storms.  

Since 2020, about 3 million barrels a day of global refining capacity has been shut permanently. That decline resulted in record refining margins for fuel makers and prompted them to virtually max out their capacity this summer. In addition to planned refinery tuneups this fall, there is limited additional capacity coming online in the U.S. for the foreseeable future. The situation means that if fuel demand rebounds, refiners will struggle to add new supplies.

“Motorists should not yet be breathing easy,” said Patrick De Haan,

head of petroleum analysis at price tracker GasBuddy.

High prices at the pump have been a key driver of the inflation weighing on American spenders, alongside soaring prices of groceries, hardware and utilities. The national average gasoline price is still almost $1 a gallon higher than it was this time last year, a political liability for the Biden administration and its Democratic allies in Congress facing midterm elections in November. 

Administration officials say their moves have helped to lower prices, pointing to President Biden’s prodding of the Organization of the Petroleum Exporting Countries and its allies, collectively known as OPEC+, to increase production, as well as oil releases from the country’s Strategic Petroleum Reserve of about 1 million barrels a day since the end of April. 

Those efforts have had some effect, analysts say, but the precipitous drop in gasoline prices is largely due to consumers cutting back on driving during the usually busy summer season because of high fuel prices. More Russian crude flowing into global oil supplies than expected, combined with an economic pullback from China and fears of a recession, have also helped ease high prices.

SHARE YOUR THOUGHTS

How have gas prices affected your driving habits? Join the conversation below.

The Biden administration’s oil releases from the SPR are set to end in coming months, and will eventually boost oil demand when the government seeks to refill its inventories. Meanwhile, OPEC+ agreed Wednesday to add 100,000 barrels of oil a day to global supplies, a relatively small amount.  

U.S. gasoline prices averaged $4.11 a gallon Friday. The last time gasoline prices averaged above $4 a gallon for a prolonged period in the U.S. was for two summer months in 2008, according to AAA data. Oil prices fell to $88.54 a barrel Thursday, the first time since Russia’s invasion of Ukraine that oil has settled below the $90-per-barrel mark. 

Refiners’ gasoline margins have halved since their record peak in early June, according to Mr. Yawger, as consumers have balked at record prices. “$5 gasoline killed the golden goose for these guys,” he said.

American drivers purchased 8% less gasoline in the week ended July 30 compared with the same time last year, according to preliminary data on same-store gasoline sales from energy-data provider OPIS, a part of Dow Jones & Co., publisher of The Wall Street Journal.

Fuel-station owners set the prices consumers see at the pump, based on what they initially paid to fill their underground tanks of gasoline and diesel. They have to sell that fuel for a corresponding amount to recoup their investments and manage a profit, which can take days or weeks, depending on how quickly they turn over their inventory.

Hussnain Gondal, an entrepreneur who runs a small chain of gas stations in Connecticut and Rhode Island, said that he expected to keep lowering prices at the pump in the next two weeks but that he couldn’t predict what would happen after that. 

“Relief may be coming, but it might be temporary,” he said.

Write to Collin Eaton at collin.eaton@wsj.com and Benoît Morenne at benoit.morenne@wsj.com