Last week the national average price for a gallon of diesel held at $1.70 per gallon, the Energy Administration reported on Monday. This follows five straight weeks of price drops, which total to a 6.3-cent decrease.

The Rocky Mountain region posted the biggest drop, down two cents to $1.815. California prices rose the highest, up 1.5 cents to $2.034 per gallon. California also is the most expensive region to fill up. The Gulf Coast posted the cheapest pump prices at $1.624, despite a slight 0.1-cent increase.