The U.S. average retail price for regular gasoline fell to $3.68 a gallon on Monday. That’s down 1.6 cents from a week ago, based on the weekly price survey by the U.S. Energy Information Administration.

Pump prices were highest in the West Coast region at 3.96 a gallon, down 4.2 cents from a week ago and marking the first dip below the 4 dollar mark since mid-February. Prices were lowest in the Rocky Mountain States at 3.47 a gallon, remaining unchanged from last week.