...to increase power output for a quick race? Wait until the gas tank is empty and fill it up 1/4 with premium gas? Or will the higher octane ratings actually be bad for the engine?

 

the higher octane simply prevents knocking. If you look into the chemistry of it it "should" create a more all at once type of burn, which should make for more efficient power. However, this is never going to be noticeable and may not even be measurable realistically. The octane rating is simply the percentage of octane in the fuel. The rest of the fuel is heptane, which pre-ignites at a lower pressure and temp.

Dont worry about running the higher octane as much as the amount you run. For best results run only enough fuel to get you through the race. weight is everything :D

 

Right, running your car with just a 1/4 tank of anything is better than running with a full tank when it comes to racing. The weight savings are 100X more beneficial than whatever octane you run. Don't let the marketing hype fool you, running higher octane in a stock car is worthless unless your car is specifically tuned for it.

My dad had a Lincoln Continental V8, car would run on 87 without knocking but would actually give better performance at 91 octane ONLY because the knock sensor would advance the timing when it detected higher octane. Our cars do not do this.

 

It is not worth running anything but the cheapest gas in our cars unless you are force inducted.