2007 2500HD 4WD 6.6 LBZ with 6speed allison

[NavyETinAZ]

I have on order a Diablo tuner from autoeverything. My question is if I tune to level 4 and drive in normal will that give me the best fuel economy or is it only level 2 and 3 that does that. I drive 95% from san diego Ca to Phoenix AZ use cruise thru Ca set for 70 and 75 in AZ. I am not towing anything.

[johan]

We did the official testing using the 65hp tune where we saw an increase of 3-4mpg. In theory based on the tunes the higher hp tunes should yield the same mileage as long as you do not romp on it. We have actually had customers reporting a greater gain using the higher hp tunes, which i would contribute to the added low end torque. But to answer your question, as long as you do normal driving the fuel mpg gains should be the same for all tunes.