U.S. gasoline prices have dipped another 6 cents due to a continuing skid in crude oil, a new survey finds, with more declines seen on the horizon.

The average price of regular gasoline dropped to just over $3.78 per gallon over the past two weeks, according to the latest Lundberg Survey. That's down more than 12 cents from a year ago and more than 18 cents below its April 6 peak, survey publisher Trilby Lundberg told CNN.

"The cause is continued erosion of crude-oil prices," Lundberg said. With crude oil currently trading at about $91 a barrel, down 11% in a month, "We will see another 5-10 cents in the coming weeks," she said.

Lundberg's California-based company samples prices in about 2,500 filling stations across the continental United States. The latest, conducted Friday, found prices were still hight in the Western states -- "but those prices are just trembling on a precipice," she said.

"We can see wholesale prices have been crashing here, and they are about to hit the street," she said.

The cheapest average gas prices were found in Memphis, Tennessee, at $3.34 a gallon, Lundberg said. The most expensive were in San Francisco, at $4.36.

Average per-gallon prices in other cities:

Atlanta: $3.45

Baton Rouge, Louisiana: $3.44

Billings, Montana: $3.76