I just made a trip from Oregon to Colorado, my best MPG was 34!!!! That was a 94 LS, and I did a little duct work my grille to the bottom of my intake and made my intake as cold as ice which was awesome!! But 34 mpg is my best!
The best I have ever gotten was 32MPG mixed highway/around town. I drove about 60-65mph cruise control and very easy around town. I usually get 26mpg if i drive the way I want to 70+mph, Opening it up when I have a chance.