U.S. gasoline prices dropped by 4 cents to $2.06 a gallon on average in the past two weeks to the lowest in more than six years, according to a Lundberg survey released on Sunday.

The price, for regular grade as of Friday, was the lowest since $2.05 in April 2009 as oil prices continued to slide, survey publisher Trilby Lundberg said.

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U.S. crude prices have dropped 17 percent in December.

Gas prices have averaged $2.48 this year, down from $3.37 last year, according to the survey of about 2,500 U.S. filling stations.

Of the cities polled, Tulsa had the lowest average retail price at $1.72, and Los Angeles had the highest at $2.71.