The average price for a gallon of on-highway diesel fell again last week, to $2.366 per gallon, according to weekly figures from the U.S. Energy Information Administration.
That was 5.6 cents less than last week's average, 94.2 cents less than a year ago, and the lowest prices since August 2005.
The lowest prices were seen in the Rocky Mountain region, at $2.272, followed by the West Coast at $2.274, where California prices averaged a low $2.251. The highest prices were in the New England region, at $2.689.
Meanwhile, oil prices fell on the New York Mercantile Exchange Monday. Crude oil for February delivery fell to $39.91 a barrel at the close of trading. The market has all but ignored the Organization of Petroleum Exporting Countries' decision last week to cut production by a record 2.2 million barrels a day.