shares of valero energy corp vlo slid 266 to 9789 monday on what proved to be an allaround poor trading session for the stock market with the sp 500 index spx falling 103 to 365504 and dow jones industrial average djia falling 111 to 2926081 this was the stocks second consecutive day of losses valero energy corp closed 4892 short of its 52week high 14681 which the company achieved on june 8th the stock underperformed when compared to some of its competitors monday as phillips 66 psx fell 241 to 7416 and marathon petroleum corp mpc fell 209 to 8954 trading volume 47 m eclipsed its 50day average volume of 40 m editors note this story was autogenerated by automated insights an automation technology provider using data from dow jones and factset see our market data terms of use