Nationwide, the price of a gallon of regular gasoline has been drifting lower by about half a cent a day over the last month, and energy analysts say that trend should continue over the next few weeks, in at least some states.
“Drivers are getting a respite,” said Rodney L. Waller, a senior vice president at Range Resources, an oil and gas company based in Fort Worth. “But it’s a tenuous respite based on all the changes in the global oil market and the opening and closings of refineries across the U.S.”
Gasoline prices are dropping primarily because of a decline in global crude oil prices, stemming from an easing of tensions in the Middle East and growing oil supplies, bolstered in recent months by the rapid return of Libyan oil exports and increased production from Saudi Arabia. Because oil is priced in dollars, the firming value of the dollar in recent weeks in the wake of the European financial crisis has also helped reduce prices.

The sluggish global economy has also reduced demand for oil and other commodities, particularly in Europe. Demand growth in China, a main driver of oil prices in recent years, has slowed in recent months. And while gasoline demand in the United States has diminished in recent months because of the soft economy, oil supply inventories recently reached a 22-year high.

Gasoline prices on the East Coast have fallen in part because one large refinery in Philadelphia that was scheduled to be closed by Sunoco at the end of June is now expected to remain open through at least most of the summer while the private equity firm the Carlyle Group negotiates to form a joint venture. Prospects for future gasoline prices in the region have also improved since Delta Air Lines bought an idled Pennsylvania refinery, which will probably produce more gasoline for the market by October.
On the West Coast, however, particularly around Los Angeles, gasoline prices have actually risen in recent weeks because several refineries were forced to suspend operations because of power failures and repairs to compressors. But those problems are expected to be cleared up by June, and energy experts expect prices to ease afterward.
The diverging refinery situations are reflected in the wide gap in gasoline prices from one coast to the other. The average price for regular gasoline on Thursday was $3.92 a gallon in New York but $4.31 a gallon in California.
The national average price for a gallon of regular gasoline on Thursday was $3.67, nearly 30 cents below the high for the year reached in early April. A year ago, the average prices stood at $3.85 a gallon.
Energy analysts say prices this summer should remain a few cents lower than last year but about 75 cents a gallon above the level in the summer of 2010. The economic effect of the lower prices is tentative because prices could easily surge again.
“Compared to 2009 and 2010, these are still stiff prices,” said Tom Kloza, the chief oil analyst at Oil Price Information Service. “People talk about this wonderful dividend, but measured against history, gasoline still represents a considerable slice of consumer disposable income.”
Mr. Kloza projected that the national average price for regular gasoline during the Memorial Day weekend would be at most only a few pennies below the current price, and would range from $3.50 to $3.75 for the rest of the summer.
Light sweet crude, the benchmark of New York trading, remained stubbornly above $100 a barrel for most of the last year. In recent weeks it has fallen to just above $90, and remained near that level on Thursday.
The spike in oil prices last year was because of the turmoil in North Africa and the Middle East, especially the loss of more than a million barrels a day of high-quality crude from Libya during the insurrection against the Qaddafi dictatorship. After easing for a few months, prices surged again early this year over fears that Iran might block supplies from passing through the Strait of Hormuz in response to tightening European and United States sanctions or the possibility of an Israeli or American attack on Iranian nuclear plants.
The sanctions have reduced Iranian exports, but increased exports from Libya, Saudi Arabia and Iraq have so far more than compensated for the drop-off in China, India and other Asian countries that have relied on supplies from Iran. Total OPEC output of oil and other liquid fuels is at a record high of 37.5 million barrels a day, despite the loss of Iranian exports.
But oil analysts warn that prices could surge again if instability interrupts production in any number of shaky producing nations. Traders were watching how a second round of talks between members of the United Nations Security Council, Germany and Iran would proceed this week, but there appeared to have been little progress. Hopes that Iran would be willing to curb its nuclear program had helped send oil prices lower, but further tightening of sanctions on Iran could send crude prices higher in the months ahead.
“If there are any problems on the supply side, as in Iran, Libya or Nigeria, then prices will be right back up,” said Michael C. Lynch, president of Strategic Energy and Economic Research. “Global inventories are not that high, and production is pretty much flat out in OPEC. A lot depends on how negotiations go with Iran.”
While production in the United States is about a million barrels a day higher than last year, now reaching 5.9 million barrels a day, several other international producers outside of OPEC are not doing nearly as well. Unrest in South Sudan has halted nearly half a million barrels a day of production. Offshore oil spills have dented output in China and Brazil, and production from the North Sea continues to decline.