Believe it or not, my major in college was chemistry for about 4 semester's. That gave me about enough knowledge to know exactly what octane is for. For those of you who don't know, Octane is not an additive to make gas burn cleaner, nor do you rarely get better gas milage. It doesn't put out more power per pound compared to 87 octane, and this I promise you....You will never pay less for 93 vs. 87. Octane is the agent in gasoline that keeps if from igniting under heat and pressure. If you know how a diesel works, they use a low octane gas, so it will ignite under pressure. Especially on 4 strokes, if you hear a pinging noise, sometimes called a labor knock in the engine, while under load, you probably need a higher octane fuel, try 89 next. If you do experience this, you will most likely get better performance from higher octane fuel. On two strokes, the fuel isn't in the chamber long enough to matter, because the spark plug fires every stroke. Some of the high end FI, DI engines recommend 93 octane, if so then use it. This is because of the design of the engines and the way fuel is inducted. This makes them more powerful and fuel efficient. To all others not hearing a knocking sound, or one's running carburated 2 stokes, stick with the cheap stuff. If you wanna **** your money away, **** it down the race track! Good luck all, and keep the hammer down! 
