Agreed. No point spending money on expensive race fuel when you can get away with something cheaper. What I might add though is street fuels have a tendency to have much higher temp fractions that don't convert to gasses at lower temps ( theses are cheap hydrocarbons that are designed to get burned in the cats on street cars) and so can hang around after a burn and detonate where as Avgas doesn't. Its designed to be able to vaporize at altitude and is very consistent as a fuel. What I've figured out from the guys that were making high hp per cube on street fuel was that it had to be run at stoich or close to stoic AFR's so as not to leave much of those to hang around and cause detonation on the next combustion cycle.
