Aug 13 (Reuters) - The discount on Western Canada Select

(WCS) heavy crude versus the North American benchmark West Texas

Intermediate (WTI) narrowed slightly on Tuesday:

* WCS for September delivery in Hardisty, Alberta, settled

at $12.60 a barrel below WTI, according to brokerage CalRock,

having settled at $12.80 a barrel under the U.S. benchmark on

Monday.

* 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 ( XOM ) 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

* Canadian crude production growth is enough to fill the

expanded Trans Mountain pipeline to Vancouver and also max out

egress into the U.S., East Daley said in a note.

* Global oil price eased about 2%, as traders grew less

nervous about the potential for a wider war in the Middle East,

with Iran yet to act on threats to retaliate on Israel for

assassination of a Hamas official in Tehran.