So when were bumping along the sub 85 plateu; How important is the energy lost in refining progressively heavier crude? Is it significant? Or is it that the energy lost in cracking/refining is provided from burning fractions that aren't useful?

I guess what I'm asking is: Is there, after cracking/refining, as much gasoline in a light sweet barrel as in a hevy crude barrel?

(Im not dumb, Oil is just not my trade....)

Two points:

  1. Cracking is an endothermic reaction.  It does take heat to raise the feed and catalyst temperatures (providing by burning the coke), but most of that energy goes into making the more energetic short chain molecules.  The only energy lost in the sense I think you mean in the cracking is actual heat loss from the equipment to ambient.  Insulation and heat recovery techniques take care of a lot of it.

  2. About the only thing you can generalize is that you will get more distillate and gasoline and less residual from any crude if you use an FCC than if you don't.
Checking out what FCC was on the wikipedia lead to some enlightening reading....

One way of phrasing what Im getting at is:
When the gasoline is in the hummers tank ready to be consumed; Is there already a larger CO2 price tag on the gasoline derived from Heavy than on gasoline from light sweet.

Heavies have more carbon and less hydrogen than lights, so more CO2.  It's not a gigantic difference, though.
And wikipedia is a good source if you want a quick look at the unit operations in an oil refinery.