WASHINGTON, D.C. --- For the eighth week in a row, diesel prices dropped in all regions of the U.S., the Energy Department reported Sept. 10.  

The average U.S. retail diesel price slumped 6.2 cents to $4.059 per gallon, a cumulative plummet of more than 70 cents from the all-time high set on July 14, the department's Energy Information Administration said.

Nonetheless, the price remained $1.135 higher than a year ago. The average price on the East Coast dropped 6.9 cents to $4.10 per gallon. The price in the Midwest slipped 5.1 cents, hitting $4.015 per gallon. The price in the Gulf Coast dropped 5.3 cents to tie with the Midwest for the lowest price in the nation at $4.015 per gallon.

The price in the Rocky Mountains tumbled 7.9 cents to $4.105 per gallon. Plunging 9.2 cents, the average diesel price on the West Coast reached $4.156 per gallon. In California, the price fell to $4.185 per gallon, a drop of 9.7 cents.