I see that this is an old thread, but I would like to spark it up again. I have an 05 3500 4 door dually with the 6 spd, and I'm seeing 33+ mpg as long as I keep my foot out of it. Is this unreal? Is the onboard computer seeing something different???

 

You mean the Lie - O - Meter?? The computers in those trucks can be anywhere from 3-20mpg off.. Hand calculate it and you will be sure to be disappointed lol Mine is off by 3mpg..