If you believe your overhead then that is part of you problem. Mine is consistently over by 1.5 mpg.

 

Gonzo, that's an incredibly high mileage number for any Ram CTD.

 

and any box will make it off even more.

i've had 2 reflashes done to my overhead computer (one was the -44 degree thing) and it's still from 2~3 mpg off on the 06

the 04, with a BDDLPP on it, was closed than the 06 with no box.

 

Well everything is Bigger in Texas Fellas.

I'm thinking 28mpg is a bit high especially with 37's, I don't want to get into a debait on i have bigger tires, less rpm blah blah blah.

But sometimes the overhead monitors are actually pretty close. On my 06 CTD Auto, it was off by 2-3mpg over. With my new 6spd, I reset it the first day I had the truck and have left it alone since (10K miles). It currently reads 15.7mpg and when I hand calculate I get 16-16.8 depending on how I drove for that tank.

So i would say that mine is probably pretty close for an average of 10k miles...

my .02 cents