Since crude feedstock represents a major portion of refinery operating costs, price volatility has a direct impact on profit margins. The following two figures show the price trends for North American, European, and Middle Eastern heavy crudes from June 2008 through mid-Sept. 2010. It is notable that in both figures, the heavy/light differentials generally widen as the average crude price increases. In the following figure, Mexican Maya traded at a $20-30/bbl discount to WTI in mid 2008 when crude oil prices were exceeding $140/bbl, but the discount has narrowed as average crude prices have come down. ...Log-in for complete content