(CNN) -- Gas prices surged nearly 7 cents over the past two weeks to reach an all-time inflation-adjusted high of $3.26 per gallon of self-serve regular, a national survey said Sunday.
The previous inflation-adjusted record occurred last May 18, when the price was $3.24 in current dollars.
The Lundberg Survey, carried out Friday, tallied prices at about 5,000 gas stations.
Despite the record price, seasonal demand is growing, said Publisher Trilby Lundberg.
"We are soaking up a surplus that existed, we're using up a cushion" as the nation enters its high-demand spring season, she said.
Though ethanol prices also jumped during the two-week period, crude oil prices actually dropped, she said.
The price of crude closed Friday at $101.84, down about $3 per barrel from two weeks prior, but the drop was not uniform. During the two-week period, the price had exceeded $110.
"If not for lower crude oil prices, the gasoline price hike would have been greater," Lundberg said. "The ethanol people, the refiners and retailers all saw slight improvements in their profit margins."
Absent further slippage in the price of crude, gasoline prices will continue their rise "as spring demand really kicks in," she predicted.
At $3.03, average prices in Newark, New Jersey, were the nation's lowest. Drivers in San Francisco, California, where the average price was $3.66, paid the most.
Part of the difference is explained by the fact that taxes account for 66.20 cents per gallon in San Francisco and just 32.95 cents in Newark, Lundberg said.
The higher cost of doing business and stricter fuel reformulation requirements in California explain the rest of the difference, she said.
Here are average prices of a gallon of self-serve regular in some other cities:
Atlanta, Georgia: $3.23
Boston, Massachusetts: $3.14
Chicago, Illinois: $3.42
Denver, Colorado: $3.12
Houston, Texas: $3.18
Miami, Florida: $3.34
Portland, Oregon: $3.40 E-mail to a friend