Last checked at 
* August WCS last trading at $12.50 per barrel under WTI
* August synthetic trading at $4.50 premium over WTI
CALGARY, Alberta, July 2 (Reuters) - Canadian heavy crudeprices strengthened on Tuesday on news of another refineryrestart, while synthetic oil prices were lifted by expectationsof constrained supply.
Western Canada Select heavy blend for August delivery lasttraded at a discount of $12.50 per barrel below the West TexasIntermediate benchmark, according to Shorcan Energy Brokers.
That compares with a settlement price on Friday of $14.25per barrel below the benchmark. Canadian crude markets wereclosed on Monday due to a public holiday.
Energy market intelligence firm Genscape reported Phillips66's 306,000 barrel per day Wood River, Illinois,refinery had returned to normal operations, adding toexpectations of increased demand.
Canadian crude prices have been supported in recent weeks byExxon Mobil restarting its 238,600 bpd Joliet, Illinois,refinery and BP Plc completing the startup of a new250,000 bpd crude distillation unit at its 413,000 bpd Whiting,Indiana, refinery.
Traders said the delay in production from Imperial Oil Ltd's Kearl oil sands project was also contributing tostronger prices.
Light synthetic crude from the oil sands for August deliveryrose to a premium of $4.50 per barrel over the benchmark,compared to settlement price of $3.00 per barrel over WTI onFriday.
Market sources said prices were boosted by anticipation oflower supply in August after Syncrude Canada Ltd said last monththat a coker at its northern Alberta oil sands project would beshut for 50 days.
"We don't know whether there is going to be an Augustproduction cut, but the market is trading like it thinks therewill be one," one Calgary-based crude trader said.
Meanwhile, Suncor Energy Inc and Nexen Inc, owned byCNOOC LTD, have reduced production at their oil sandsoperations after parts of the Enbridge Inc pipelinesystem that serves the region were shut down last week followingan oil spill.
On Monday Enbridge said it reopened the northern part of its345,000 bpd Athabasca pipeline at a reduced operating pressure.
