HOUSTON, Sept 29 (Reuters) - A flurry of gasoline import cargoes helped push California gasoline prices down from July's 2015 highs, but the continued shutdown of a major Los Angeles-area refinery on top of autumn planned work at other plants could bring more spikes by Thanksgiving, experts and traders said.
Multiple import cargoes of gasoline and gasoline components docked in Los Angeles this month to help beef up the strained southern California market missing about 20 percent of its normal supply with Exxon Mobil Corp's 149,500 barrels- per-day Torrance refinery out since mid-February.
A few more cargoes are on the way, including the STI Aqua slated to arrive on Tuesday and the BW Shinano from the United Kingdom on Wednesday, according to vessel tracking data available on ThomsonReuters' Eikon.
The influx has bolstered stocks ahead of autumn maintenance, easing Los Angeles wholesale gasoline differentials from July's $1.35 premium over U.S. benchmark RBOB on the New York Mercantile Exchange to about 30 cents over the futures price on Tuesday.
Los Angeles-area pump prices that surpassed $4 a gallon for the regular California-specific blend in July retreated about a dollar.
"The armada has died down a bit, which is very normal when the price signal drops back down," said Gordon Schremp, senior fuels specialist at the California Energy Commission.
However, California remains short on gasoline with the Torrance outage and demand up 2.5 percent in the first half of 2015, he said.
The nation's largest gasoline market's pump prices are normally about 40 cents a gallon higher than the rest of the lower 48 states, largely because of California's boutique blend that costs more to make.
The state's average pump price is still 70 cents or more above the national average of $2.28 a gallon - and 83 cents higher in Los Angeles, according to AAA Fuel Gauge Report.
Traders said upcoming maintenance at several refineries, including an 80-day shutdown of a gasoline-making fluid catalytic cracking unit at Chevron Corp's 245,271 bpd plant in Richmond expected to begin next month, will again squeeze supply as imports wane and refiners draw down stocks.
"I predict two or three spikes and retreats in autumn," a West Coast gasoline trader said.
The November switch to winter-grade gasoline with higher vapor pressure could mitigate spikes, Schremp said. That switch allows refiners to blend in more butane, making more gasoline per barrel of crude.
Reporting By Kristen Hays; Editing by Chris Reese