What kind of mileage are you guys out there getting with an 04 5.7 QC 2wd, 3.92, with 20's? I have only done magnaflow muffler and removed the resonator and my computer says 13.4mpg for the last week. I have driven about 300 miles and about half highway and half streeet. I follow speed limits and try not to stomp on it. What are your guys' computers/calculations saying? Seems a little low for half highway but maybe not. LMK THANKS

 

Try selecting reset while on the mpg screen and see what the new readings get you. The sensor becomes less and less sensitive to mpg changes the longer its been since last reset, this is to give you a more accurate average reading. So its a good idea to hit reset if your driving conditions change and you want to see what the new averages are going to be.

 

It gets less sensitive becasue it is averaging the miles you just drove with all the other miles you've driven. However, this is a more accurate reading. If you reset your computer all the time you will get wild readings like 20MPG while going down the interstate.

It's ok to reset it every now and then, but not after only 300 miles, unless you just want to feel better. Either way, your gas is being used at the same rate.

I get about 13mpg doing mostly city driving and being heavy on the peddle with my Hemi, it has about 400 miles on it. That's with no mods.

 

Resetting frequently during break in is a GOOD idea, and to leave it WILL NOT PROVIDE a more accurate reading. If you do not reset often, your improving fuel economy is masked by the crummy fuel economy you got 300 miles ago. Therefore you are not getting an accurate reading as your fuel economy is constantly improving over break-in. At this point in time the trucks average over alot of km's is not important, its improvement however is, and the only way to notice this is do reset often to clear old "tainted" mileage info.