(CNN) -- U.S. gas prices jumped more than 11 cents per gallon over the past two weeks, but may be peaking as the price of crude oil holds steady, according to the latest Lundberg Survey.
The average price of U.S. regular gasoline rose to $3.93 per gallon, up from just over $3.81 in the last Lundberg Survey on March 9. But survey publisher Trilby Lundberg said prices declined about a penny per gallon in California, where fuel costs are typically the highest, and crude oil prices have remained fairly steady in March.
"If crude oil prices do not spike again, then gasoline prices will be peaking very soon. They may already be doing so," Lundberg said. "It will depend almost entirely on crude, as usual, but if they stay where they are, the peak may well turn out to be under $4 per gallon."
Average U.S. gasoline prices have climbed by 36 cents per gallon over the past year. But with demand still relatively weak and nearly one-fifth of U.S. refinery capacity idled, the U.S. gasoline market "is not strong enough to spike on its own," Lundberg said.
"The market is well supplied and looking well supplied into the future," she said.
The latest Lundberg survey canvassed about 2,500 filling stations in the continental United States on Friday. The cheapest average gas prices in Lundberg's were in Tulsa, Oklahoma, at $3.58 per gallon, while Chicago had the most expensive at $4.56.
Average per-gallon prices in other cities:
Albuquerque, New Mexico: $3.64
Baton Rouge, Louisiana: $3.73
Newark, New Jersey: $3.62
Portland, Oregon: $4.03
St. Louis: $3.97
Sacramento, California $4.23