The average price of a gallon of regular-grade gasoline fell 7 cents nationally over the past two weeks to $2.56.
Industry analyst Trilby Lundberg of the Lundberg Survey said Sunday that the drop comes as crude oil prices drop and flooded refineries on the hurricane-battered Gulf Coast return to operation.
Lundberg says she expects further price cuts as refiners make cheaper "winter grade" gasoline.
The current price is 27 cents above where it was a year ago.
Gas in San Francisco was the highest in the contiguous United States at an average of $3.11 a gallon. The lowest was in St.Louis at $2.20 a gallon.
The U.S. average diesel price is $2.76, down a penny from two weeks ago.