dossfatboy

I just got the SCT x4 and since I have put 325/65/18 tires I changed the rev per mile. My first question is the revs per mile, per the tire size calculator is 582.2 and the X4 gave me a 580 and a 585 option. I chose the 585 however the speedometer is now off by more than before when it was stock rev. Is there an option to enter the actual rev per mile?

Second - I stayed with the 87 octane and noticed no difference. Which should I chose?

Third - I see shift options and don't know if I should stay with stock or change. I don't do towing at the moment and I drive pretty normal. I really don't get on it, well maybe a little at times, but not to much. Any thoughts?

Truck is a 2006 FX4 4x4 5.4

Thanks for any help..

99S351

I have an SCTx4. If I remember correctly I chose the lesser number, that was closest to my rev per mile. It is still off a little bit, but dyno tuning and a legit speedo calibrator is going to correct it.

Fill your truck up with 93 oct, use the tune for that and towing mode, that is where I noticed the largest increase. Firmed up my shift points to.

My only other mods are a K&N and Borla Exhaust to turn my 35s.