Summer of 2014, I worked a job that was about 283 miles from home, so I rented an apt and drove home on the weekends. I have a Superchips tuner for my 2005 Dodge Magnum Hemi car that allowed me to tune the engine for 87 octane or 91. I was using so much gas at that time that I tuned it for 87. According to my rough calculations, I did get a little better fuel mileage tuned for the 91 but I was saving about $12/week running 87. But, my car has MDS which shuts off 4 cylinders when cruising to save fuel. Driving down I95 in South Carolina at 80mph with the cruise set, it didn't take much of an incline for the computer to switch the 4 cylinders back on. I thought it was missing at first before I realized that it was switching the 4 cylinders off and on. That demonstrated a slight hp/torque decrease in the 87 tune. I set it back to a 91 tune afterwards. I like the tuner because it did improve the throttle response noticeably and increased the hp/torque by 12hp/15 ft. lbs. according to the Superchips site and it felt like that was about right. The site has a dyno graph for my engine showing the results.