The average U.S. price of regular-grade gasoline has dropped 3 cents per gallon (3.8 liters) over the past three weeks to $2.63.
The price is 20 cents lower than what it was in mid-July.
However, industry analyst Trilby Lundberg of the Lundberg Survey says Sunday she expects the trend to reverse after Saturday's drone attack on Saudi Arabia's key oil processing facility.
There was no immediate impact on global oil prices from the attacks as markets were closed for the weekend, but analysts anticipate a price spike when markets reopen Monday.
The highest average price in the nation is $3.62 a gallon in the San Francisco Bay Area.
The lowest average is $2.11 in Baton Rouge, Louisiana.
The average price of diesel is down a penny since August 23, to $2.99 per gallon.