It allows an engine that is designed to run on higher octane to run at it's full potential. If your engine only requires 87 or 89 octane, it will NOT increase horsepower. It will also clean no better than a lower octane fuel, they all have detergents. It is only on the TV commercial where it does this.

If Toyota recommends lower octane, then that is best. Look in your owners manual or google for the recommended octane.

Unless the owner's manual specifically states to use high octane fuel, you are just throwing money away. I would go back to regular unleaded. Switching back and forth between octanes does not harm anything. If it runs good on regular, stick with regular. Every 6 months or so, add a bottle of injector cleaner to a full tank.

Nope. Higher octane gas is more resistant to pre-ignition (which can happen in today's high-compression engines).

Octane is not a cleaner, and it's not going to provide you with more horsepower.

You use the gas the car was designed for. For a GT, it's 91.

Nope. Higher octane just prevents pre-ignition. It has the same power and same cleaning additives as regular. Read this post on premium gas

http://ricksfreeautorepairadvice.com/pre...

3M Total Fuel System Cleaner will do a better job of cleaning intake valves, combustion chambers and fuel injector nozzles with no more than 14 gallons of gas in the fuel tank.

It's available at NAPA and Carquest.

I have a Toyota Celica GT 2003. I usually use the 93 because i heard that it'll increase horsepower and clean out the engine. I've only use the 93 for about two months, what happen if i convert back to regular gasses and which gas are best for the car? Will using regular gasses damage the car in long term?