Okay, after 4 tanks, Hand calculated mpg with correction for tire size using gps on my truck is 14.2mpg average with about 50/50 city/highway driving. DIC put it at 14.9 mpg. I run my six gun on level 3. Before I was always between 14-15.5 mpg. I don't think I ever broke 16mpg. I have not done enough towing to see what that is going to be like. I am going to try and bump pressure up to 80lbs for 2 tanks to see if it makes a difference. Just out of curiosity really... Oh yeah, tires look brand new still with over 1k on them. I get many comments on them:D
So yes I lost a little fuel efficiency, but not bad at all. So so far absolutely no drawbacks to this modification! I will be going to Hatfield Mccoy in Nov with a 16ft trailer and a bunch of quads for a 400 mile trip. That will give me a better measure of towing mpg.
Later
Steve

:nopics:
I want to see them! :D

For your viewing pleasure!
http://www.dieselplace.com/forum/showthread.php?t=330071

Thanks for the link. That is one good looking truck. I wish I could afford the 19.5's. Have always liked the way they look!

Just curious , have you reset for tire size and did you run a aggressive tread design on old tires? I put 19'5s on and my milage improved

Just curious , have you reset for tire size...

...Hand calculated mpg with correction for tire size using gps

I corrected mine w/ EFILive when I installed them. The only problem is, I installed the EFILive at the same time and switched to SoCal's tow tune at the same time so I don't know how the tires affected it. I do know that I went from 6 up to ~8-8.5 towing heavy.

i get about 14.5/15.5 mpg when towing and i do not run it easy at all