An Exxon station is shown in Keller, Texas, in this July 25, 2007 file photo. Exxon Mobil Corp. on Friday, Feb. 1, 2008 posted the largest annual profit by a U.S. company—$40.6 billion—as the world's biggest publicly traded oil company benefited from historic crude prices at year's end. (AP Photo/Donna McWilliam, file)