@mik
I am sure Alberta crude can elaborate on this fact
For the most part he’s right about the refineries. As for the imported heavy crudes, they are sold at a discount into the US and then blended with domestically produced light crude to produce gasoline for the US market or re-exported as upgraded medium crude. In the case of synthetic crude produced here we upgrade it so it can be transported by pipeline and the oil companies resell it at a discount to either their parent company in the US - for example, Imperial Oil Canada selling it to its US parent company, Exxon-Mobil - or, like Canadian owned Suncor or Cenovus, to their US subsidiary at a discount. In the end the US refiners are the ones making the big dollars as their feedstock is always discounted.