Heavy Oil Discount Holds Steady

* WCS for September delivery in Hardisty, Alberta, settled at $12.25 a barrel below WTI, according to brokerage CalRock, having settled at the same level on Thursday after narrowing for five straight trading sessions

* Markets worry that any Canadian rail stoppage would cut prices of Canadian crude due to lack of takeaway capacity

* The expansion of the Trans Mountain pipeline has, however, limited the reliance on rail to transport crude oil from Canada to the United States

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

* Global oil prices settled down nearly 2% on Friday, little changed on the week with Brent crude below $80 a barrel, as investors tempered expectations of demand growth from top oil importer China.

(Reporting by Arathy Somasekhar in Houston; Editing by Mohammed Safi Shamsi)