As said many times. Gasoline and diesel is the same. The only thing that makes it different is the additive package added in at the terminal.
No. There is a difference on some things.
What is most likely happening is that Shell just doesn't market diesel to that particular region. It could be that they are swapping barrels and the gas isn't even from a shell refinery just a shell additive. Could be a number of other causes.
Well - I'm pretty sure that gasoline and diesel aren't literally the same.
There are of course going to be measurable differences. However, the vast majority of gasoline sold in the United States is a commodity that meets certain requirements for its classification. It's still a fungible commodity, where it's effectively interchangeable to the point where any base fuel meeting the requirements that's finished with the additive package can legally be marketed as a branded product. And often the base fuel is commingled with equivalent fuel from multiple refineries.
And for the ironies of ironies, Shell has a distribution terminal in Southern California, which is probably the largest local market for gasoline and diesel in the United States. But they have no refinery in Southern California.
I found a picture of one of these pumps:http://forums.tdiclub.com/showthread.php?t=364070
I don't have that much experience with diesel, but I was under the impression that they deal with far fewer additives than with gasoline. What makes it "branded" would seem to be less specific than the detergent additive packages used in branded gasoline.