91 octane vs e85 in flex fuel Tahoe/suburban?

[Fless]

So you’re running e85 year round even in sub zero temps? It gets VERY cold here in NESD

Yes. Gets pretty cold here, too, and that's when I drive the Hoe the most 'cause 4x4. And I'm at least 4000 ft higher; you can't be more than 2k' in elevation, are you?

 

[Marky Dissod]

I hear good things about chevron with Techron

Chevron with Techron has actually lowered its concentration of poly ether amines lately, but at least it still has PEA in it.
Don't fear the other stuff, they all come highly recommended from the folks at Bob Is The Oil Guy, plenty of PEA.