UNITED STATES - JANUARY 29:  Valero Energy Corporation's gasoline desulfurization unit is seen at its West Plant in the Corpus Christi, Texas refinery, January 29, 2006. The desulfurization unit cost $115 million to build and started operating in March 2005. Valero's Corpus Christi West refinery was completed in 1983.  (Photo by Eddie Seal/Bloomberg via Getty Images)