Maximizing LLY fuel mileage

[Fireman Fred]

I recently purchased a 07 Classic 4x4 stock drive train and 285 tires. I get 14+- in the city and 16ish unloaded on the hywy. my camper is 8k and i get 9 to 10 best I recently pulled a boat (9-10k) flat land and got 6mpg is that to be expected? should i be looking for somthing wrong? my speed was approx 68 and 1600 rpms. i had the GM place look at it and they say it is in spec's. she does not struggle at all just poor milage, any thoughts.

[mr. monte]

your 285's are killing you

my '07 classic w/ the LBZ can squeak-out 22 mph unloaded keeping it at 55-60 mph, all stock except for a 4" turbo-back system, EGR block-off, and diesel kleen added to every tank, as soon as you go over 60 mph, mpg drops quick

[JohnC]

Is your odometer corrected for the 285 tires? You may be going more miles and more mph than you think, both of which would make the mileage seem low.

[dannomatt]

Some random thoughts.
My take on the D.I.C.: (Don't) Trust, but verify. Mine is seldomly better than .5 MPG off.
My MPG: 15 - 17, with my best now being 18. (2005 C/C, L/B, 2WD, all stock - except tires - See below)
ULSD: The change-over was before I owned my LLY. But I know that the Cat 3126 in my M/H lost 2 - 4 MPG due to ULSD.
Tire size vs. MPG: I lost 2 - 3 MPG due to the 265/75-16s I installed on my truck. With the 245s, I always got 17 - 19, with the best being 20.8.
'DPS' in Van Nuys, Ca. recommends the 'Predator' hand held programmer that can install/uninstall different tuning maps for power - economy - etc. Customer claims of 1 - 3 MPG.
Regarding above: I'm chicken. Too many horror stories of codes being flashed due to re-programming. (In all fairness, very few ugly stories are about the Predator - But I'm still too anal to experiment)
Dan