This is for all those of you out there that are constantly asking if you really need premium (92+ octane) in you turbo wrx, baja, forester, or STI. Share this with your friends and disregard at your peril.
Ok, let me explain about forced induction (turbo or supercharging) and how it relates to octane ratings. First of all the octane rating of gas is it's resistance to what's called detonation. Higher rating=more resistance=better burn When you're running any forced induction application this becomes critical in that you start running a lot more air into the engine. Remember, all that a turbo does is force more air into your engine so that there is more air to burn. Now if you run any gas with too low of an octane rating you are basically now running too lean on the engine. It's just as if the engine wasn't getting enough fuel. Hence detonation. Very bad juju. Too much air+not enough/wrong fuel=BOOM! Forget knocking, we're talking about destroying your pistons, and blowing the head on the motor. Trust me, this information came very painfully to me.