Thanks for the help rjaro7

OK, thank you. I think I may have to play with it a bit and see if the 87 tune or the performance (93) tune have a bid difference in mileage. I won't be pulling much anymore so I can probably go down. Did you use 87 with the mpg booster?

The MPG booster is designed for a minimum of 91 octane?? or the performance tune?

OK Diablo, at the risk of posting a dumb question. I just want to make sure I understood the posts correctly. The new MPG tune is based on 87 octane gas correct? I am currently running the performance tune for better mpg, using the 93 octane and since I am retiring next summer, I would love to save ...

got it done, thank you

I bought new "larger" tires for my 09 Chevy 2500 . I see the instructions on how to change to tire size but do I need to reinstall the the performance program or can I just go in and change the tire size?