Our trip to the NebSHO meet in KC I averaged 30.2mpg, 73mph all the way there, and some slower stuff going through KC and some in town driving. That was with 100 miles (1/4 Tank) off of a full tank of 91oct, then topped the tank off with 87oct.
I typically get 24-26 on 91oct with about 20% city, 60% at 58mph cruising, and 20% 63mph cruising. Yeah I stick to my speeds, and nor cruise control involved. 58mph & 63mph are two different highways, one to work, the other to the girlfriends house.