The national average price for a gallon of diesel slid 1.9 cents to $2.792 for the week ending May 6, according to the Energy Information Administration.

Prices dropped the most in the Lower Atlantic region, down 2.7 cents to $2.735. That is also the cheapest region in which to fill up. But not all regions enjoyed a rollback at the pump: the Rocky Mountain area logged the largest increase, up 0.7 cents to $2.995, making it the most expensive region for diesel.

For more information, go to http://tonto.eia.doe.gov/oog/info/wohdp/diesel.asp.