The average price of a gallon of gasoline in the United States fell 9 cents in the past two weeks as refiners and retailers reduced their profit margins to sell more fuel, according to a Lundberg survey released on Sunday.

Regular grade gasoline fell to $2.35 per gallon in the Sept. 25 survey from $2.44 on Sept. 11, when the previous survey was taken. It has tumbled 36 cents over the past five weeks to the lowest level since late February.

Compared with one year ago, the $2.35 average price was $1.03 a gallon lower.

The latest decline came despite crude oil prices having strengthened in the last five weeks, survey publisher Trilby Lundberg said.

"The main reason for this is that both refiners and retailers have reduced their own profit margins on gasoline, which had last month been temporarily wider than usual, for the sake of chasing sales," she said.

While 2015 gasoline demand is projected to be the highest ever on record and show 2.6 percent growth over the previous year, gasoline supply is even greater.

Unless a crude oil supply problem creates a dramatic spike in oil prices, "we will probably have further cutting at the pump," Lundberg said.

Gasoline prices could slip another 5 to 10 cents in coming weeks and continue to decline as winter nears, Lundberg said.

The lowest average price per gallon in the lower 48 states was in Baton Rouge, Louisiana, at $1.92, and the highest in Los Angeles, at $3.06.