Stabil for the fuel. No reason to put 93 octane in. Octane number is the fuels resistance to pre-ignition not a better fuel. So the lower number actually ignites easier and burns better in a lower compression engine. You should run the lowest octane fuel you can without pinging. If your engine pings move up one grade until it stops. That whole regular, premium bit is a sales gimmick.

I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!