Flat U.S. gasoline prices mask sharp spike in California

Oct 7 (Reuters) - The average price for a gallon of gasoline in the United States rose less than half a cent over the past two weeks, masking a decline in most regions and a sharp spike in California prices, according to a widely followed survey.

Gasoline prices averaged $3.8375 on Oct. 5, up from $3.8338 on Sept. 21, Trilby Lundberg, editor of the Lundberg Survey, said on Sunday.

Prices were down about 3 to 12 cents in most markets except the West, she said.

While the overall U.S. average gas price was flat, the California average price at the pump jumped to $4.4992, up 38.79 cents per gallon in the same two-week period ending Oct. 5, Lundberg said.

Even while U.S. crude oil prices eased during that time, refinery outages sparked higher prices, causing shortages at some gas stations.

On Oct. 6, the average price in California for a gallon of gasoline hit a record at $4.614, according to AAA.

But two gasoline price indicators - one in California market proper and the other in the West region - showed signs that prices were set to ease, Lundberg added.

The spot price in Los Angeles dropped 40 cents between Oct. 3 and Oct. 5, from $4.2495 to $3.85 per gallon.

"Unbranded rack (gasoline), the second-most sensitive to changes in supply," also saw a decrease, according to Lundberg.

"That price on Oct. 4 in the Western region was $4.0284. On Oct. 5 it was $3.9075, so that means it dropped by a bit over 12 cents in one day."

Additionally, Exxon Mobil Corp's Torrance, California, refinery was back up and running after a power outage.

The current U.S. average for a gallon of regular gasoline at $3.8375, is still higher than a year ago, on Oct. 7, when the average price was $3.4192, Lundberg said.

"People are not looking at the date and calculating whether it's interesting or not interesting, but it's not great for those really watching costs, or those trying to get around in this economy to find a job," Lundberg added.

According to the survey, which tracks 2,500 gas stations nationwide in the lower 48 U.S. states, the most expensive gas was in San Diego, at $4.55 a gallon. Drivers in Jackson, Mississippi, again paid the least at $3.43 per gallon, and two weeks a gallon of gas there cost an average $3.52.

(Reporting By Jeanine Prezioso; Editing by Maureen Bavdek)

((jeanine.prezioso@thomsonreuters.com)(+ 1 646 223 6241)(Reuters Messaging: jeanine.prezioso.reuters.com@reuters.net)(on Twitter @jeanineprezioso))