The average price of a gallon of diesel fell for the second week in a row, dropping to $4.602 per gallon, the lowest it's been since May.

Weekly retail on-highway diesel price figures released Monday by the U.S. Energy Information Administration showed the price fell 11.5 cents per gallon from the previous week. The highest average price was in the New England region at $4.806. The lowest was in the Midwest at $4.518.

The national average is now 59.5 percent higher than during the same week in 2007, according to the American Trucking Associations' economic department.

Meanwhile, crude oil prices rose slightly on the New York Mercantile Exchange Monday, closing just under $125 a barrel. The Associated Press reported that "In [a] sign traders think oil prices may have peaked, the U.S. Commodity Futures Trading Commission said that for the first time in 17 months, a majority of commodities speculators are shorting oil prices - or betting that prices will fall."