Thanks for the link to data on refinery inputs. What I think that this illustrates is that there was been limited [if any] improvement in the ability of U.S. refineries to handle higher amounts of heavy / sour crudes.

If production is shifting toward these heavier sour grades, "Houston we have a problem" [an appropriate city from a quote coming completely out of context. Depending on your degree of faith in the U.S. Government feel free to substitute "Washington" for "Houston".] :-)