I have had my '04 LLY for about 3 weeks now (less than 1000 miles). With 100% city driving, stop and go, very hot with AC going full time, my first two tankfuls have yielded only 13.5 MPG. Is it true what everybody says about mileage improving after a while. If not, what could be causing my poor mileage compared to the majority of everyone else? One reason why I paid $1000's more for the diesel was the promise of better mileage. Other than that, I love my new truck. Thanks

Mine is getting better. I also bypassed the EGR which seems to have helped quite a bit. But we are still in the testing phase with that mod.

I have an 04 LLY DRW 3500 CC. My previous truck was an 01 2500HD CC Duramax. It started out around 15 MPG in town and was at 17-18 when I traded at 40K miles. Also added a hard bed cover. My LLY has 5K on it now and gets about 13 MPG in town. Has not improved yet.

Lots of shorter trips - 5,500 miles on my truck and I get around 16 mpg. Around 14 mpg when pulling our 3 horse gooseneck. Not using AC.

I drive 15miles 1 way to work daily, some 2 lane hilly southern Oh roads.. about 6miles 4 lane at 55.. 03 LBY a few mods.. Get consistantly 15-16 seems to be holding with 16k miles.. Now on Interstate at 65.. cruise as high as 22mpg but mostly 20.5 - 21http://www.dieselplace.com/forum/smileys/Geek.gif