WASHINGTON, D.C. --- The average U.S. retail diesel price slipped 6.5 cents to drop below $4 a gallon for the first time since April 7, according to a Sept. 24 report from the Energy Information Administration.

At $3.958 per gallon, the national average price reflected a cumulative drop of more than 80 cents from the all-time high set on July 14.

The East Coast diesel price slipped 6.1 cents to $4.021 per gallon, but this region was the only one where the average price remained above $4 a gallon.

In the Midwest, the diesel price dropped 4.2 cents to $3.931 per gallon. The average price in the Gulf Coast slumped another 8.7 cents to become the lowest in the nation at $3.924 per gallon.

The price in the Rocky Mountains dropped 7.7 cents to $3.964 per gallon. In the West Coast, the average price plunged 11.3 cents to $3.943 per gallon -– falling below $4 for the first time since March 10. The average price in California declined 10.2 cents to $3.951 per gallon.