I have a 2012 dually 4x4 gmc bone stock. I drive it decent and get only 13-14 mpg. about 12000 miles on it . I also have an 03 GMC with bully dog, 4 inch exhaust, hi flow intake and it gets 20+mpg. any ideas on the 12 to get better mileage?

 

Get rid of the DPF. Will almost guarantee a 3+ mpg increase.
Efi-live will be needed for tuning, and will help mileage also. Stock intake is fine.

Water/meth inj will help. Downpipes are rumored to help, manifolds/uppipes as well.

 

^^^ pretty much sums it up.

 

with any duramax it will be hard to beat your MPG numbers. a DPF delete wont hurt but with only 12000 miles the engine is far from broken in and will typically get a little better when it is.

i would give it some time and wait for the warranty to expires first

 

I ran a 2000 3/4 ton Chevy with a 6.5 duramax. After 37,000 km mileage went to 24 mpg highway and 20mpg when in town and that was pulling trailers so it should increase when broke in.

 

That sounds about right. The tune is what gives you the gain in MPG. A DPF does not cost you as much fuel mileage as you would think. We have compared tuning LML's with and without the emission equipment. Turns out the deleted trucks only get another 1 MPG at the most. Your truck should only regen once a tank in most cases. Check out what Nick (Founder and Owner of DuramaxTuner.com) writes about Regen fuel consumption;

4. How much extra fuel does regen take?

My best guess comes from the mileage adjustment I see under steady state operation. For instance. My trip this weekend averaged 19.7 MPG mixed over 700 miles. The truck entered regen at 700 and regen-ed for 40 miles. At the end of regen the DIC showed 19.2 MPG. If I'd done the 740 mile trip without regen at 19.7 MPG I would have used 37.56 gallons. At 19.2 MPG, I used 38.54 gallons - a difference of about a gallon or 2.6% more fuel.

My suggestion is to take a look at the LML SPADE. If you would like a quote I can PM you one.