Do you all run E load range tires on your 2500 Duramaxes? Do you have to/is it highly recommended? Can you run D load range tires? What are the disadvantages of doing so?

It makes a difference if you tow or haul much weight. Check the load ratings on the tires against how much weight you are going to load the truck with. If you don't plan on putting anything very heavy back there, a "D" rated tire will be OK.;)

I tow an ~8k trailer daily.

The weight rating of some D's are equal to some E's.
I believe the big difference is the side wall. E's are stiffer. D's aren't as stiff and will make the truck feel squirrelly.

I run 8 ply D-rated Bfg a/t's and am very happy with the ride, but I'm not sure how much I would pull with it.

The weight rating of some D's are equal to some E's.
I believe the big difference is the side wall. E's are stiffer. D's aren't as stiff and will make the truck feel squirrelly.

Exactly. The drivability and handling of an "E" will be better & safer. Especially if you have much weight on the tongue, which you probably do with 8,000#.

You could get by with the "D" rated tires if the specific tire weight rating is not exceeded, but the "E" would be a better choice if you haul daily.

load range d - 285 carries more weight than your oem load range e -245 .

hauled large trailers for thousands of miles with out incident, and benifited from better fuel economy with a taller tire

Unless you change the size of the oe tire which is the 245\75r16 tire which is a 10ply rated tire @3042lbs at 80psi, there is no benefit to going with 8 ply unless they are a lot cheaper???? The 8ply tire max air pressure is 65psi & will have a lower weight rating, also will affect the way the truck handles as it is a lighter tire & was designed for the 10ply.....