i've been using Chevron for long time. in my TL it requires premium, and on my 4R, i put 89. back in the Shell's day, like Thai mentioned about the "V power", i only pump premium if i have to go to Shell.
gas mileage is pretty good, well of course it has to do with driving habit.
but on my most recent trip in the 4R, A/C on, 4 adults and 1 kids in the whole trip and average of 75-80mph, from Sacramento to Santa Cruz Mystery Spot, then Santa Cruz beach boardwalk. then stuck in traffic for 1 hours, then head to Mountain View and back to Sacramento, total of about 340 miles plus or minus. i used about 20 gallons of gas, which means there's still about 2 gallons reserved. i am happy of what my 4R did, and it's a 4X4 V8.