ATLANTA (CNN) - Gasoline prices decreased about 6 cents over the past two weeks, according to a survey published Sunday, but the survey's publisher said the trend is unlikely to continue as spring and summer approach.

The Lundberg survey found that the average price of self-serve regular as of Feb. 24 was $2.24 per gallon, representing a 9-cent drop over the past five weeks.

But "I believe we can expect these price cuts will end soon," said publisher Trilby Lundberg. Crude oil prices surged by about $2.50 per barrel Friday with the news that a Saudi oil facility was targeted for a suicide bombing attack, even though the attack was unsuccessful. If that jump remains uncorrected, she said, it will translate into about a 5-cent jump in gas prices.

In addition, Lundberg said, now is the time that refiners draw on gasoline stocks as they conduct routine maintenance and repair in preparation for warmer weather and increased gasoline demand.

Also, "This year's new fuel reformulation requirements make the spring and summer blends already costlier" than last year, she said. The convergence of previous and new environmental regulations -- lower levels of sulfur allowed, for instance, and use of ethanol rather than the additive MBTE -- will add to the cost and tighten the supply.

The survey found the lowest cost of gasoline was in Portland, Ore., where a gallon of self-serve regular cost $1.99, and the highest cost in Honolulu at $2.59.

Some other prices:

-- Atlanta, $2.10

-- Los Angeles, $2.45

-- Houston, $2.12

-- Chicago, $2.32

-- Boston, $2.20

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