I won't put E85 in my Denali. Supposedly it eats up seals quicker. The benefit in SOME parts of the country is that it is easy to find and cheaper than gas. The problem is that it uses 25% more gas so you will be stopping for gas 25% more often. In the end you'll spend about the same, except for potential fuel system problems later on. With most fuel systems the fuel pump now sits on top of the tank with the filter. Guess how much that costs to replace $800-2000 depending on vehicle.
As far as what to do with high gas prices? When you bought the vehicle did you consider that prices would go up? My Denali gets about 18-20mpg on the highway but I didn't expect it to be a gas miser, not at 6000lbs, 6.2 L V8 and shaped like a brick.
For those desiring a trade in remember that big SUVs are not selling that well now for the same reason why you want to sell it. That means you will lose trade-in or resale value so in the end you are going to lose thousands of dollars on the sale, buy say an Acadia and decrease your fuel bill by at the most 25%. I say at the most because my Denali was actually more efficient than an Acadia I had for some trips. If the road is not dead flat or going down the Acadia will use 5th or even 4th gear. Yukon doesn't care until you hit about a 5% grade.