(CNN) -- U.S. gasoline prices dipped by nearly a nickel per gallon ahead of the Thanksgiving holiday as cheaper crude and slumping demand kept pressure on costs, the latest nationwide survey found.
The average price of self-serve regular at U.S. filling stations fell to $3.38 per gallon, down 4.82 cents in the past two weeks, according to the new Lundberg Survey. Gasoline prices have now dropped more than 8.6 cents per gallon over the past month, survey publisher Trilby Lundberg told CNN.
The slide comes despite an upward trend in the price of West Texas Intermediate crude, the benchmark product for the U.S. oil market. But that increase is being offset by a decline in other varieties of crude, including Britain's benchmark Brent crude, Lundberg said.
And demand for gasoline has been in a long-term skid, she said.
"There's two reasons for that," she said. "One is the continuing bad economic conditions keeping underemployment high, and the second reason is we've just left daylight saving time." With the time change, sunset comes earlier -- and "people eschew driving in the dark when they can," she said.
The latest Lundberg Survey canvassed about 2,500 filling stations on Friday. It found the highest average gas prices in the Lower 48 states in San Francisco, at $3.78 per gallon; and the lowest in Albuquerque, New Mexico, at $2.96.
A sample of average per-gallon prices in other parts of the country:
Billings, Montana: $3.53
Portland, Oregon: $3.63
St. Louis: $3.06
Salt Lake City: $3.27