The Lundberg Survey of fuel prices released Sunday puts the price of a gallon of regular at $3.42, down 13 cents from two weeks earlier and down 25 cents in the past month.
Costs have seen similar drops in midgrade, now at an average of $3.58 a gallon, and premium at $3.70.
Diesel fell seven cents to $3.85 a gallon.
Of the cities surveyed, Albuquerque, N.M., had the nation's lowest average price for gas at $3.07, and perennial price leader San Francisco had the highest at $3.81.
In California, the lowest average price was $3.71 in Fresno. The average statewide was $3.77, down 11 cents in the two-week span.