As summer nears, gas prices accelerate

LOS ANGELES, California (CNN) -- Gas prices zoomed nearly 13 cents during the past two weeks to an average of $1.63 per gallon of self-serve regular, a national survey reported Sunday.

The survey, taken April 6 and April 20, tallied prices at 8,000 gas stations. The increase was most dramatic in Chicago, where prices rose 23 cents to $1.91 during those two weeks, said Trilby Lundberg, publisher of the Lundberg Survey.

But San Francisco's $1.95-per-gallon average was the nation's highest. Salt Lake City, Utah, at $1.43, was lowest.

Lundberg said tight supplies were the cause of the increase, not crude oil prices, which have remained stable over the past two weeks.

Refiners typically close part of their operations for maintenance "to make sure there are sufficient supplies of the various formulations in time for summer driving," Lundberg said.

Demand usually starts to pick up in May, though this year's demand is likely to be weaker than it was last year because prices are higher, she said.

At $1.48 per gallon of self-serve, gas prices were 15 cents lower this time last year.

Lundberg Survey

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