Heavy Oil Discount Narrows for Fourth Straight Session

* WCS for September delivery in Hardisty, Alberta, settled at $12.40 a barrel below WTI, according to brokerage CalRock, having settled at $12.60 a barrel under the U.S. benchmark on Tuesday, for the fourth trading session in a row

* Canadian heavy crude differentials have gained support this month from some U.S. Midwest refineries restarted operations after unplanned shut-downs in July.

* Exxon Mobil restarted select units at its 251,800 barrel-per-day refinery in Joliet, Illinois, three weeks after it lost power following a storm, the company said last week.

* However, Exxon reported a unit upset at Joliet on Saturday and Sunday, according to Illinois Emergency Management Agency

* Global oil prices settled 1% lower on Wednesday after U.S. crude inventories rose unexpectedly and as worries eased slightly that a wider Middle East conflict could threaten supplies from one of the world’s major regions for crude production.

(Reporting by Arathy Somasekhar in Houston Editing by Marguerita Choy)