Expect a bit of a shock if you fill up your gas tanks in Southern California this week.
The average price of a gallon of regular gasoline in the state has jumped 23.4 cents since last Monday, according to the AAA Fuel Gauge Report.
Most of the spike has been driven by the state's southern counties.
Los Angeles and Long Beach, for example, are averaging $4.017 a gallon, up 24.8 cents over the past week.
Orange County gasoline is averaging $4.002 a gallon, up 26.1 cents since last Monday.
The Southern California averages compare to $3.859 a gallon today in San Jose and $3.723 in the region around Modesto.
So, what gives?
"Refinery maintenance," said Denton Cinquegrana, executive editor of the Oil Price Information Service. OPIS collects prices daily from more than 100,000 retail outlets across the U.S. and supplies the AAA with its averages.
"California has a lot more planned refinery maintenance than it usually has at this time of year," Cinquegrana said. "And most of that is concentrated in Southern California."
Cinquegrana added that some of the maintenance was deferred from the fourth quarter of 2012, when refineries kept operating to boost supplies after California prices hit a record average of $4.671 a gallon in October.
The bad timing about all of this is that it also figures to run in to the state's early switch to summer blend gasoline, which starts in March. That is much earlier than most of the rest of the nation.
"It's also the summer blend that is more expensive," Cinquegrana said, "because it can't contain the cheaper, junk additives, like butane" that are used in colder weather, winter blends.
"You could see Southern California prices getting back up to $4.25 by then," he said.