That's not very low. I don't remember the tank size for sure and am to lazy to search it, but I think its close to 7 gal. Defineatly not 2.5.
I will be interested to see how the tuner does.
I am going to leave mine stock until the warranty runs out as I am really happy with the performance and mileage is good enough that I can enjoy the peace of mind the warranty gives me when out on the road.

The DEF tank is 5 gallons.

FYI... The 2011 is the first year to use software which makes permanent record of any parameter changes within the software. The ECM/PCM records and stores the last 10 calibrations in the memory. It also shows the OEM, VIN specific, CVN (calibration verification number). The TCM records and stores max HP and torque values and shares this info with the ECM via the CAN bus. For any powertrain warranty work to be performed, the dealer must send an electronic snapshot of this info to the factory, via the Tech II scan tool.

What does all of that mean??

Installing a programmer and then removing it before taking the truck in for warranty work doesn't work anymore. Resetting parameters with a Tech II doesn't work, as the last 10 calibrations are stored. The Tech II snapshot is required by the factory... the decision about warranty work isn't up to anyone at the dealer. Once any of the above info is found to be non-correlating, a warranty block for your VIN goes into the GM Global Connect database... Your 5 year/100,000 mile warranty is gone forever.

I'm leaving mine alone...

Ditto..peace of mind, and 100k warranty in tact is more important.

We have not had any problems with our 11 GMC to date with 28k on her...my buds 11 Chevy has been in 6 times for def problems like I posted back a few posts.. Good Luck WaterBoy.

Well maybe the tuner isn't the way to go then.. Its not really the HP increase that I was wanting, more MPG was the goal. Thinking now maybe I'll stick with the exhaust and intake and keep putting miles on hoping for better economy. My iphone App is showing 12mpg now at 4100 miles. I just filled up last week and I'll be hand calculating it so see if theres a difference.

And the reason I was saying it held all of the 2.5 gal jug was that if the tank was still over half full and the level sender was misreading, it wouldn't have held the full 2.5 gal. I guess they don't fill the tank from the factory. Has anyone heard of any DEF tanks getting a hole knocked in it? We spend a lot of time on dirt roads (not MY truck, but our others) and the rockers take a beating with the gravel. That tank seems to be in a HORRIBLE location..

My HD2500 gets 14-14.5mpg with a mix of around town and short highway trips. 20-20.5mpg with strictly highway driving. My truck has 33k miles, and I'm thinking that's as good as the mileage is going to get. Remember that one regen cycle kicks the crap out of the average economy. Another thing, is that a dually has a shorter tire on it than a single wheel truck, so your effective gear ratio is lower... ie: worse for fuel economy.

Haven't checked mine lately and I am usually pulling something. The 17 mpg was staight highway going to ponca running 85ish. I get about 10ish pulling the 43'toyhauler. I have about 30K on it now. I don't always get the oil changed when I should so I have bought alot of the 2.5 gallon DEF's. They seem to last a really long time. Longer if I'm not pulling.
Wasn't trying to talk you out of the programer at all, I may put one on after my warranty. But for now I am happy with the mileage considering it is a dually and has tons of power.
And after my experience with the Ford, I really like having a factory warranty.

You can say THAT again...