shares of valero energy corp vlo slipped 633 to 13161 monday on what proved to be an allaround poor trading session for the stock market with the sp 500 index spx falling 388 to 374963 and dow jones industrial average djia falling 279 to 3051674 this was the stocks fourth consecutive day of losses valero energy corp closed 1520 short of its 52week high 14681 which the company reached on june 8th the stock underperformed when compared to some of its competitors monday as phillips 66 psx fell 458 to 10144 and marathon petroleum corp mpc fell 570 to 10217 trading volume 64 m eclipsed its 50day average volume of 50 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