Recently, prices of high-sulfur crude oils have been declining relative to low-sulfur crude oils. Rising crude oil exports from OPEC members that produce mostly medium-sulfur or high-sulfur crude oils, also called sour crude oils, and higher natural gas prices have contributed to lower prices for sour crude oils relative to low-sulfur (sweet) crude oils. Sour crude oils typically sell at a discount to sweet crude oils because they must first be treated with hydrogen to meet low-sulfur fuel specifications. They also require desulfurization to avoid damage to refinery units. In recent months, however, sour crude oil ... (full story)