Oil prices haven't hit bottom yet.
Extending a dramatic decline this year, U.S. crude dropped to a new five-year low Monday.
The U.S. benchmark, West Texas Intermediate, fell 4.2% to $63.05 a barrel, the lowest since July 2009.
Oil and gasoline prices have been driven lower in recent months by a North American shale oil boom and a sluggish global economy. The combination has increased supplies and depressed demand.
The average price for a gallon of regular gas nationwide fell to $2.668 on Monday from $2.769 a week ago, according to Auto Club.
The California average was $2.981 a gallon, down from $3.058 last week.
Declining prices have been a boon to U.S. consumers, especially middle- and working-class Americans whose gasoline expenses account for a significant portion of their paychecks, analysts said.