Valero, refiners lead oil-sector stocks lower By: MarketWatch September 17, 2012 at 11:40 AM EDT Citi analysts argue it’s time to lock in strong summer gains by shares of independent petroleum refiners. Read More >> Related Stocks: Baker Hughes Inc ConocoPhillips Halliburton Co Marathon Petroleum PHLX Oil Service Sector Index Phillips 66 Schlumberger Ltd Valero Energy