Originally Posted by JPop

I have had my best mpg results with my Superchips Flashpaq on my truck using the premium settings and calculated with pencil and paper. I always seem to get better mileage on the premium settings than with regular or Superchips Mileage XS setting. I have not ran enough fuel to make any comparisons on my Jeep as I just haven't had it long enough.

Additionally, the tire size issues really comes into play if someone is doing the math for their tire size change and runs an automatic transmission. As shift points are determined by throttle position, rpm and speed, which all too often can lead the PCM hunting and searching for gears. Less time with the converter locked up and more torque management to soften shifts leading to poor fuel mileage.

That said, I think as much as a 5-10% increase in fuel efficiency is obtainable with premium settings and premium fuel, and potentially more if the PCM was scratching it's head with shift points. Those have been my observations with the Superchips and my truck and again I haven't ran enough fuel through the Jeep to verify.

Also, with gas at $2 a gallon it's pretty much a wash with additional mpg and the additional fuel cost. As the fuel prices go up it certainly makes more sense and was a no brainer with fuel at $4 a gallon last summer. Best of all, when you stomp it you get that little extra power.