The national average price for a gallon of diesel took a 3.3-cent dip last week to average $2.156, marking the fourth straight week of rollbacks, according to the Energy Information Administration.

All regions posted a price break, but the Rocky Mountain region enjoyed the largest, with a 6-cent cut to $2.207. Prices were the most stable in the Lower Atlantic region on a 2.2-cent decline to $2.119. California remains the most expensive region in which to fill up, despite a 5.9-cent cut to $2.373. The Midwest saw the cheapest pump prices at $2.097 on a 3.2-cent drop.