My tunes:

1. 89 performance (daily driving)
2. 89 tow (for hauling the boat down to lakes Madison and Poinsett which we did this weekend :2thumbs: )
3. 91 performance (for when the wife wants to drag race the tow vehicle... ;) )

I just tried to come up with the best combination of utility and economy for the octane available in this area, and that was my magic 3.