I know I read over and over that the levels of Octane used in cars these days doesn't matter. For the last 3 fill-ups I decided to try the mid-grade unleaded which is 89 octane. In my region you can get 87, 89 and 92 grade gasoline. Well folks, my MPG has actually gone up some to 27.2 average from 26.7. The most noticable is the throttle response. I do notice a more reactive throttle response. In order to see if this is just my imagination. I am going to switch back to 87 octane for the next 3 tanks and see.. Anyone else do this? or use a higher grade fuel in their Fusions/Milan? :?