Okay, guys. Let me tell you this from the perspective of a guy who has a B.S. in Mechanical Engineering and an M.S. in Aerospace Engineering and has taken classes on this very thing:
Higher octane gas *only* helps you if you have a high-compression engine (or maybe if you have a truck pulling a lot of weight up a big mountain). Higher octane gas merely has more heavy, long-chain hydrocarbons in it, which makes it harder to ignite. What this does for you is prevent the fuel/air mixture from prematurely igniting from the compression stroke of the piston (this is what is called knocking). If you do not have a high-compression engine, you do not have a need for high octane gas, since 87 (or maybe 89 in some applications) is not going to pre-maturely ignite in our stock/nearly stock protege engines. Octane rating is *not* in any way a rating of how "clean" the gas is - only how "heavy" it is.
Patrick