NEW YORK—Whether or not any bubble has burst, Americans now live in an economy where the prospect of a gallon of gas for less than $4 is cause for relief.

That barrier may be broken as early as this weekend, as a two-week nosedive in crude prices begins to ripple out to gas stations nationwide.

The national average for a gallon of regular pulled back to just above $4 a gallon and oil tumbled to its lowest point in weeks Friday on the belief that prices have yet to reflect just how badly demand has deteriorated in the United States, the world’s thirstiest oil consumer.

Prices at the pump are poised to dip even further, and could cost as much as 25 cents less by Labor Day, AAA spokesman Geoff Sundstrom said.

“People say typically prices shoot up like a rocket, fall like a feather. But this time ... it looks like it’s different,” Sundstrom said. “The retail sector is interested in bringing these prices down as fast as they can to stimulate business in their convenience stores.”

In the trading pits, oil continued on a two-week sell-off. Light, sweet crude for September delivery fell $2.23 to settle at $123.26 a barrel in on the New York Mercantile Exchange. Earlier the contract dropped as far as $122.50, its lowest point since June 5.

Many analysts say the market’s momentum points to further declines. Crude has fallen in seven of the last nine sessions, and is down more than 16 percent from its peak above $147 a barrel earlier this month.