Shares of Murphy Oil (MUR - Get Report)  and Diamond Offshore (DO - Get Report) slid Monday as crude oil prices dropped to $40 a barrel. Both Murphy Oil and Diamond Offshore (DO - Get Report) tumbled to the bottom of the S&P 500. But Murphy stock has managed to climb about 14 percent year-to-date, as crude rebounded from 2016 lows of roughly $26 dollars a barrel. Meanwhile, Houston-based Diamond Offshore shares are up just about 0.5 percent on the year.