Diesel continued to drop for the second week in a row, down 7.3 cents to a national average of $3.021 a gallon

, according to data released Monday by the Department of Energy. This is the largest one-week decline in nearly a year and a half, the DOE reported.

Diesel took its first dive in seven weeks last Monday, when the fuel fell 3.3 cents. Prior to the dip, trucking's main fuel gained 18.8 cents over six weeks, reaching its highest level since about November 2008 at $3.127 a gallon.

This week's average was 74.7 cents higher than the same week last year.

The Central Atlantic and West Coast regions had the highest averages across the country, at $3.165 a gallon and $3.162 a gallon, respectively. Meanwhile, averages got below $3 in several areas, including the Gulf Coast and Lower Atlantic, which had the lowest averages. In these areas, diesel averaged $2.977 and $2.981 a gallon, respectively.

Crude oil prices were up slightly Monday, despite a strengthening dollar and lower stock prices, according to reports by MarketWatch. Crude rose 17 cents, or 0.2 percent, to settle at $70.21 a barrel on the New York Mercantile Exchange, according to published reports.

However, crude has been on the decline for the last three weeks, and Monday's gain hasn't offset the $20 a barrel loss since May 3, Dow Jones reported.