Since May 2 the national average price has fallen 23.6 cents and is at its lowest level since March 7.
Average prices in all regions plunged in the latest week, led by a 9-cent drop to $4.146 in California and 8.7 cents to $4.069 on the West Coast excluding California.
The national average price is 93.2 cents higher than a year ago. The record diesel price was $4.764 in July 2008.
For diesel price information, click here.