I know most refineries are 50 plus years old made only to separate Heavy or Light Sweet but cannot alternate inbetween the 2.
Example on Gulf Coast of Texas many refineries take "Heavy" Canada Tar Sand or Venezuela kinda oil the domestic production is exported because lack of refineries process that oil.
Wouldnt technology have changed in same time frame that a refinery can alternate inbetween multiple grades of crude.
Or perhaps heavy and light sweet be mixed together a refinery designed set halfway inbetween to process that