WCS is a major heavy, sour grade of crude oil produced in western Canada.

WCS serves as a benchmark for all Canadian heavy crude, with active spot markets at its primary gathering hub in Hardisty, Alberta as well as at key downstream crude centers in Cushing and Houston.

WCS is typically a blend of bitumen from the Western Canadian oil sands with diluent comprised mostly of light naphtha. The diluent is key to reducing viscosity to a level that makes it possible to move through a pipeline. 

WCS is consumed by refiners in Western Canada, but its end markets is the refiners in the US Midwest, which have invested heavily in conversion capacity to be able to run WCS in large quantities. Additional barrels typically move further south to the US Gulf Coast, where it competes with other heavy grades, mostly imported from Latin America. Some volumes are also exported through the Gulf Coast to as far away as Asia.  The other major export route is westward on the Transmountain pipeline to the Pacific coast at Vancouver, BC. From there it is exported by ship to refiners in California, and more recently, to refiners in Northeast Asia, especially China.