Been runnung premium in the r/t makes a huge difference in the milage from 12 to 18 so worth it actually. Just filled her trailblazer with 93 see if it does the same.
My 89 TBI runs better on 89 than 87, even has a marking on the tank neck for 89. Wifes Stinger runs ok on 89. We had a Mazda 3 a few years back, that car mfgr. actually gave you HP ratings for the different octanes, quite a bit with that one