Correct me if I'm wrong but I believe they make deisel from a heavier part of the crude oil than gasoline. So diesel production would compete with the fuel oil production needed for the winter while gasoline would not.
Catalyic cracking allows for some of the heavier fractions to be made into gasoline.  Therefore, heating oil production competes with diesel, jet fuel, AND gasoline production.
Sorry for spelling "catalytic" incorrectly.  I was typing way too quickly.