[74 thing]

Yep techrolene concentrate, gumout regane and seafoam are all good at getting rid of the carbon build up.

Higher octane burns slower that is why it is recomended on higher compression engines. New state of the art systems do have so many sensors that the computer will retard the timing to compensate for the lower octane gas but performance will suffer. There are other systems like safegard which is a knock sensor and adjusts each cylinders timing to fire just before detonation so you get the most performance out of your engine.

I would recommend using what your owners manual suggests for a daily driver.

Another unkown is that the mid grade is mixed at the pump/nozzle since gas stations only have tanks for regular and premium.