At some point it will still detonate on the crap they call gas nowadays. I wouldn't go past 11.0-1. If I built it to where it was even questionable I would add 110 fuel to the mix. I actually add some 110 to my Dart that has no compression issue because it runs better. I use nothing but 110 in my yard two-stroke engines because they won't run on the crap from the pump.