(AP) — The average U.S. price of regular-grade gasoline has plummeted 22 cents a gallon 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. The average gas price has dropped 40 cents in the past three months.

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.

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

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