If your car is tuned for 93 octane fuel, and you put in race gas (97-105 octane), would anything bad happen or would the car just operate the same as if it had 93 in it? I know what happens if you put in a lower octane than whats it tuned for (not good), but I never heard of any discussions pertaining to if you put higher in.

 

Not at all, unless your crazy rocket fuel is leaded or something, the car will run perfectly. I remember reading somewhere that it might even make fractionally less power because the fuel's entire potential energy is not being used, ie extra octane is taking up the space of heptane, which is the part that actually gives the fuel its energy. But I might be wrong.

 

Higher octane = withstands more compression before detonation. Which usually means it also burn slower, so it might make a tad less power on a lower octane tune.