Fuel prices surged across the nation Thursday, with regular gasoline in North County hitting yet another record and diesel shooting up 30 cents in a single week.

The dollar's long decline has been one of the driving forces behind the steep, three-month rise in prices. Oil hit yet another trading record, $126.98, on Tuesday and edged up from a dip Wednesday to end trading Thursday at $126.09. Many investors buy commodities such as oil as a hedge against inflation when the greenback falls; also, a weaker dollar makes oil less expensive to investors overseas.

That has helped to feed the sustained rise in gasoline prices, and the rising wholesale prices have led gas-station owners to wonder how long they'll stick around. Four North County stations have closed down since the beginning of the year; other gas station owners and a consumer advocate say wholesale prices are largely to blame.

At North County pumps, regular gas hit a new record, an average of $3.94, for the 13th week of the past 15, according to a weekly survey by the San Diego-based Utility Consumer Action Network. The average price of diesel fuel rose 29 cents, to a record $4.75 per gallon.

"This will have an immediate impact on food prices," said Charles Langley, the advocate and analyst who conducts the survey.

Diesel is used to fuel most trucks, trains and ships, and is a large part of the reason prices of food and consumer goods are rising so fast. Nationally, diesel prices jumped 3.6 cents Thursday to a new national average of $4.455 per gallon, according to a survey of stations by AAA and the Oil Price Information Service.

Analysts said oil's surge followed partly from anticipation of strong demand for diesel fuel in parts of China ravaged by Monday's earthquake. Gas prices, meanwhile, advanced past a national $3.77 per gallon. Prices are 67 cents higher than a year ago, and many analysts think they could rise as high as $4 on a national basis in coming weeks. Consumers in many areas are already paying that much, or more.

Oil futures were also following heating oil prices higher. Heating oil is closely related to diesel fuel, and is often traded as a proxy for diesel. Some investors are concerned that damage to China's natural gas infrastructure will lead to a temporary spike in demand for diesel. Heating oil futures for June delivery rose 4.92 cents to $3.667 on the New York Mercantile Exchange.

Mike Lynch, president of Strategic Energy & Economic Research Inc. in Winchester, Mass., doubts the impact on distillate prices from the earthquake will last long. Natural gas pipelines are easy to fix, and there have been recent indications that Chinese demand for oil is waning, he said. Still, until repairs are made, "you can imagine a lot of diesel generators firing up," Lynch said.

Lynch said gas prices will probably peak around $3.85 to $3.90 per gallon on a national basis just before the Memorial Day weekend.

"I don't think we'll go much higher than that," he said.

Demand for gasoline has been sliding since January, and many analysts think American consumers' spoiled appetite for fuel will eventually pull prices down. However, that theory could prove wrong if continued dollar weakness pushes oil to new records.

Oil prices may be more volatile in coming days as investors square positions ahead of the June contract's expiration next week.

In other Nymex trading Thursday, June gasoline futures rose 3.89 cents to $3.2193 per gallon, and June natural gas futures rose 4.2 cents to $11.64 per 1,000 cubic feet.

In London, June Brent crude rose 90 cents to $122.76 per barrel on the ICE Futures exchange.

The Associated Press contributed to this article. Contact staff writer Chris Bagley at (760) 740-5444 or cbagley@nctimes.com.