The average U.S. price of regular-grade gasoline dropped 9 cents per gallon (3.8 liters) over the past three weeks, to $2.84.
Industry analyst Trilby Lundberg of the Lundberg Survey says Sunday that lower crude oil prices contributed to the drop at the pump.
The price is 17 cents lower than what it was a year ago.
The highest average price in the nation is $3.94 a gallon in the San Francisco Bay Area.
The lowest average is $2.27 in Baton Rouge, Louisiana.
The average price of diesel fell by 4 cents since May 17, to $3.12.