Drivers of diesel trucks spent an average of $8.40 more this week than last week to fill their tanks. A report by the Department of Energy states that the average price of a gallon of diesel continued to climb this week, reaching $1.323 per gallon on April 8, which is 2.8 cents above last week at this time and 16.9 cents above the price six weeks ago. Numerous reasons are stated for the price increase, including the fact that the Organization of Petroleum Exporting Countries (OPEC) has maintained production discipline in the face of an upturn in demand, hoping to keep the price per barrel within the $25 - $28 range. Other explanations include the continuing unrest in the Middle East, which may have added as much as $6 per barrel to the price of crude oil, as well as the switchover to gasoline production for the summer driving season, which reduces the supply of diesel.