LBZ Fuel Mileage

[BigRabbitMan]

For reasons unrelated to mileage, I am going to be using a Banks tuner in my FMC motorhome conversion to the LBZ (there is a thread in the Conversion forum). The tuner has an "economy" setting.

Does anyone have any experience with using this setting in a Banks tuner. Any thoughts on a percentage improvement in mileage that would be reasonable to expect vs the stock setting. I will be basically running "loaded" all of the time as the coach weighs about 14,500 lbs.

[Scooby]

I am wanting to get the best MPG out of my new to me 2007 2500 CC LBZ with 248k on the clock. I drive MOSTLY unloaded, in Florida, and im only seeing 16 -17 mpg. The tires on the truck are very new 285/75/16 , and I do correct for larger tire size in mileage calculations, and use GPS to compare. Im wondering how much the larger tires effect the fuel mileage, and what difference I would see if I went back to the 245/75/16 size that came on the truck. From what I have found, my tires are 2" taller, so it raises the truck 1 inch. I have always heard lower truck = better mileage, but I dont know how much 1 inch will change things. Any experience / suggestions would be greatly appreciated.
I am also planning to install a DSP5 and EFI tunes at some point. I want the economy tune, and the ability to switch to more power when I need it. I think this would give the best results for better mileage, over messing with the tires.