CAMARILLO, Calif. (AP) — The average U.S. price of regular-grade gasoline has plummeted 22 cents a gallon (3.8 liters) over the past three weeks, to $2.51.

Industry analyst Trilby Lundberg of the Lundberg Survey said Sunday that falling crude oil costs are the main reason for the decrease at the pump.

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The average gas price has dropped 40 cents in the past three months.

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The highest average price in the nation is $3.58 a gallon in the San Francisco Bay Area. The lowest average is $1.91 in Tulsa, Oklahoma.

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The average price of diesel fell 9 cents over the past two weeks, to $3.18.