Murphy USA (MUSA) , a leading independent retailer of motor fuel and convenience merchandise in the United States, continues its uptrend. The stock closed Thursday's session at $535.50 after setting a new 52- week high of $536.09 earlier in the day. As shown in this chart, with the advance, MUSA shares are up more than 50% since the start of the year, handily outperforming the sector and the S&P 500. The company has also fared better than other downstream operators like Phillips 66 (PSX) and Marathon Petrol ...