By Nichola Groom LOS ANGELES, Oct 4 (Reuters) - Pump prices in California soared this week as key Golden State refineries were disrupted at a time of low inventories, putting prices on track to break a record set in the summer of 2008. The state average for a gallon of regular gasoline jumped to $4.315 on Thursday, 18.2 cents higher than last week and 49 cents higher than a year ago, according to AAA data. At a 76 gas station in Santa Monica, property developer Binky van Bilderbeek, 39, said he was shocked. "Going up by 20 cents is remarkable. Shocking to be honest," said van Bilderbeek, who drives a Ford F-150 pickup truck. "If it goes to more than $5 a gallon I'll have to seriously consider getting a hybrid truck." A Costco Wholesale Corp gas station in Marina del Rey was closed on Thursday due to supply issues, a security guard there said. Costco could not be reached for comment. In recent weeks, California refineries have dropped production in anticipation of switching over to a "winter blend" of gasoline next month. At the same time, a power outage at Exxon Mobil Corp's Torrance, California refinery on Monday and a shutdown of the crude distillation unit at Chevron Corp's Richmond, California refinery contributed to the tight supplies. Phillips 66 said a planned maintenance was under way at its 120,200 barrel-per-day (bpd) San Francisco-area Rodeo refinery. Chevron also said a pipeline that carries 85,000 barrels per day of crude oil from the state's Central Valley to refineries in the San Francisco Bay area has been closed since mid-September due to the presence of elevated organic chloride levels in the crude stream. "It's a series of unfortunate events," said Tom Kloza, chief oil analyst for Oil Price Information Service, which compiles the price data for AAA. "This is not something that is going to last for months. This is something that is going to last for days or weeks." Still, Kloza said it was likely that the record California average gasoline price of $4.61 a gallon, set in June of 2008, would be broken. "We are looking at the highest California prices ever," he said in an interview. The California Energy Commission said in a statement that it had increased monitoring of the gasoline market and was advising consumers to combine trips, shop around for gas and keep their vehicles tuned up with properly inflated tires. At a Chevron station in the Brentwood section of Los Angeles, the price for regular gasoline went up 20 cents a gallon overnight. "My car is a gas guzzler, it's sucking me dry," realtor Marty Halfon said as he filled up his 1992 Mercedes. "I'm in real estate, I live in my car. I'm held hostage. LA doesn't have public transportation and the problem is you have to drive everywhere you go. So what do you do? Stay home?" Prices in the Los Angeles spot market for October-delivery gasoline reached a record $1.75 a gallon on Thursday over NYMEX RBOB gasoline. Valero Energy Corp on Thursday said it was temporarily withdrawing from the Los Angeles spot refined products market to assure supplies to its branded and unbranded retail stations the company supplies.