The average U.S. price of regular-grade gasoline plunged 19 cents over the past two weeks to $4.86 per gallon.
Industry analyst Trilby Lundberg of the Lundberg Survey said Sunday that the continued decline comes as crude oil costs also fall.
"Assuming oil prices do not shoot up from here, motorists may see prices drop another 10-20 cents as the oil price cuts continue making their way to street level," Lundberg said in a statement.
The average price at the pump is down 24 cents over the past month, but it is $1.66 higher than it was one year ago.
Nationwide, the highest average price for regular-grade gas was in the San Francisco Bay Area at $6.14 per gallon. The lowest average was in the city of Baton Rouge, Louisiana, at $4.19 per gallon.
According to the survey, the average price of diesel dropped 13 cents since June 24 to $5.76 a gallon.