The national average retail diesel price kept falling during the week ended Dec. 17, dropping 4.6 cents to $3.945 a gallon, according to the U.S. Department of Energy’s Energy Information Administration. The latest weekly price is 11.7 cents above the same week last year.

Diesel prices fell in all regions, led by a drop of 7.2 cents in the Rocky Mountain region. With numerous decreases in recent weeks, the average price of $3.866 a gallon gives the Rocky Mountain region the unusual distinction of having the second-least expensive diesel in the country after the Gulf Coast region at $3.847 a gallon. The Rocky Mountain region also was the only one where diesel prices currently are lower than they were a year ago. The highest diesel prices on average were in New England at $4.155 a gallon.

Complete diesel price information is available on EIA’s Website.