Refinery stocks have been in a market sweet spot for some time. IBD's Oil & Gas-Refining/Marketing industry group outperformed the Nasdaq and the S&P 500 in each of the past four years. So far this year, the group is up 18% vs. mid-single-digit gains for the major stock indexes. Three things are currently helping refinery stocks . First, no refinery has been built in the U.S. since 1976. Although existing refineries have expanded capacity sharply