Canada's heavy crude differential to U.S. futures widened on Tuesday as the monthly Canadian crude market trade cycle began:
* Western Canada Select (WCS) heavy blend crude for August delivery in Hardisty, Alberta, last traded at $13.60 per barrel below West Texas Intermediate (WTI) oil, according to Net Energy Exchange. On Friday, WCS for August delivery settled at $13.30 a barrel below WTI crude futures. * Tuesday was the first day of the monthly trading window when liquidity picks up. It runs for roughly 2-1/2 weeks from the first of each month until the day before Enbridge Mainline pipeline nominations are due. * Storage levels in Western Canada remain at elevated levels, and some producers are struggling to find buyers for all of their crude, a trader said. * The government of Alberta, Canada's main crude-producing province, eased oil production curtailments for August on Thursday, setting the limit at 3.74 million barrels per day, compared with 3.71 million bpd in July. * Light synthetic crude from the oil sands for August delivery last traded at a 25-cent premium to U.S. crude, larger than Friday's settle of 10 cents per barrel over WTI. * U.S. oil futures fell nearly 5% even after OPEC and allies agreed to extend supply cuts until next March, as weak manufacturing data had investors worried that a slowing global economy could dent oil demand. (Reporting by Rod Nickel in Winnipeg, Manitoba; Editing by Peter Cooney)