i don,t know how all of ya have got away with doing this but it is not good for small engines to be run on racing fuel run them long enough and you will BURN the VALVES . Most small engine companies will tell you to run the lowest octang 87.
I put 94% nitromethane mix in a power washer. The pump went out and it cost too much to repair it. And there is no sence in tossing a good running briggs motor. It would only run at full throttle, after about 30 seconds it blew a yellow smoke out the top of the carb, coughed, backfired, and never would restart.