A national survey shows gas prices fell 3.8 cents in the last two weeks.

The average price of a gallon of regular gasoline at self-serve stations was $3.66 Friday. Mid-grade was at $3.80 and premium was at $3.92.

That's according to the Lundberg Survey of 5,000 gas stations nationwide, released Sunday.

"Demand falls seasonally every September, and is also declining this year because of high prices and the weaker economy," Lundberg said. "Retail prices should continue to slide, but are unlikely to go back to $3 a gallon absent a global collapse in crude oil demand."

Diesel was at $4.16.

Gas was cheapest in Wichita, Kan., at $3.29 for a gallon of regular. It was most expensive in Honolulu at $4.15.