FILE - This Wednesday, March 21, 2012 file photo shows prices at a Shell station in the Wilshire district of Los Angeles. Why the seasonal spike in gas prices during spring? It’s the time of year refineries reduce output to repair equipment and start making a cleaner, more expensive blend of gasoline for summer. The average price of gasoline could surpass $4 per gallon nationwide as early as mid-April 2012. Strong global demand, heightened tensions with Iran and a smattering of supply disruptions have kept crude oil prices elevated for months. (AP Photo/Reed Saxon, File)

Associated Press
FILE - This Wednesday, March 21, 2012 file photo shows prices at a Shell station in the Wilshire district of Los Angeles. Why the seasonal spike in gas prices during spring? It’s the time of year refineries reduce output to repair equipment and start making a cleaner, more expensive blend of gasoline for summer. The average price of gasoline could surpass $4 per gallon nationwide as early as mid-April 2012. Strong global demand, heightened tensions with Iran and a smattering of supply disruptions have kept crude oil prices elevated for months. (AP Photo/Reed Saxon, File)
FILE - This Wednesday, March 21, 2012 file photo shows prices at a Shell station in the Wilshire district of Los Angeles. Why the seasonal spike in gas prices during spring? It’s the time of year refineries reduce output to repair equipment and start making a cleaner, more expensive blend of gasoline for summer. The average price of gasoline could surpass $4 per gallon nationwide as early as mid-April 2012. Strong global demand, heightened tensions with Iran and a smattering of supply disruptions have kept crude oil prices elevated for months. (AP Photo/Reed Saxon, File)
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