EPA. The Ultra-low Sulfur Diesel requirements for highway diesel have moved to non-road diesel/fuel oils. It is coming for gasoline in the near future.
When I lived in New England, it seemed that heating oil was cheaper than gasoline. I can see if the new EPA regs require reduction in sulfur how that might change.
But there was another reason the cost of heating oil was lessened: Congress passed a law each year to give a reduction in heating oil costs. this was designed to favor the liberal northeast.
Since you seem to be able to manipulate google pretty good, can you find out what is its status? Are we still subsidizing Yankees?