between 89 and 93 Octane Gas. I can not. I switch between a tank of 89 and 93 Octane. I know the computer will automatically adjust but honestly I have as much black carbon on/in the tail pipe no matter if I use 89 or 93 Octane. I even put one of the 100+ Octane Boosters snake oil bottles in the tank no difference. Pick up and idle is the same. So what is you reason to spend the extra cents per gallon at the pump?