"This has been a true price crash," said Trilby Lundberg, publisher of the Lundberg Survey.
The average price of a gallon of regular gasoline is $3.38, down nearly a dime over the past three weeks, Lundberg said.
"This crash began back when refining problems around the country were being fixed, one after the other, at the same time that our seasonal gasoline demand was shrinking," she said.
Crude oil prices have also dropped after having risen steadily.
Prices at the pump should drop even more in the coming days, as refiners cut how much they're charging distributors and retailers, Lundberg said.
The national average is about 8 cents higher than the average a year ago.
The survey tallies prices at thousands of gas stations nationwide.
Long Island, New York, had the highest average in the latest survey, at $3.85. The lowest average was in Memphis, Tennessee, at $3.04.
Here are average prices in some other cities:
• Boston - $3.59
• Baltimore - $3.34
• Atlanta - $3.27
• Baton Rouge, Louisiana• - $3.11
• St. Louis - $3.05
• Salt Lake City - $3.40
• Los Angeles - $3.68
™ & © 2012 Cable News Network, Inc., a Time Warner Company. All rights reserved.