Has anyone head of using racing fuel, say 100 octane, every once in a while (maybe once a month) in order to clean out your fuel system. Supposedly the higher octane works as a cleaner.

Unless the higher octane gas has cleaning detergents, it will not clean the fuel system differently than any other octane gas with similar detergents. Octane does not have a cleaning effect.

How about cleaning out the inside of the pistons since it burns "cleaner"

Unless the higher octane gas has cleaning detergents, it will not clean the fuel system differently than any other octane gas with similar detergents. Octane does not have a cleaning effect.

Nope. There was someone recently on the board whose action item was to find 100 octane and maybe mix it with half a tank of say, 93.

I'd answer it, but sometimes people get an idea and once you have the idea, it's hard to let it go and say, "Nope, that's a bad idea." But, it's good thinking to try to improve your car. History and known experience would simply offer to get good fuel, don't run it too low, put in some additives to help clean the injectors, change the fuel filter as needed and generally stay inside the box. Here's the reasons why not:

http://www.bajajusa.com/High%20Octane.htm

http://wiki.answers.com/Q/Will_using_a_higher_octane_fuel_increase_the_car's _miles-per-gallon_rate

And a quiz :D:

http://dnr.louisiana.gov/sec/EXECDIV/TECHASMT/ecep/trans/b/b.htm

It's on a Honda Forum, LOL:

http://www.8thcivic.com/forums/showthread.php?t=6087

If your really concerned with the amount of carbon build up you have-find an indy somewhere that has a motor vac system and use that to clean the motor out.
Most racing gass that I know of has lead in it to aid the valve seats-lead is the last thing you want in your engine--it will ruin your 02 sensors.

Many have used Seafoam to clean out the carbon from the fuel system and engine with great success (gettin ready to use it myself so I'll post my experience). The only difference with the higher octane will be a better burn resulting in less carbon buildup but in order to clean out the soft carbon, you need some sort of detergent to break it down first as pointed out already by M Powered and Bimmerfiver. +1 Dudes...

If your really concerned with the amount of carbon build up you have-find an indy somewhere that has a motor vac system and use that to clean the motor out.
Most racing gass that I know of has lead in it to aid the valve seats-lead is the last thing you want in your engine--it will ruin your 02 sensors.

+1