MPG Question.

from my research anywhere from 15-22 depending on the mods done,your driving habits and the terrain you drove

a 4 inch exhaust will def help keeping smaller tires will too(stock size) but i still doubt that you would get mid 20s unless your truck was a single cab 2wd.not trying to be a jerk but i plan to do this with my v10 cc/sb fx-4 and it wieghts about 8k.not to mention your added more wieght with the cummins,ive read they are a good 300 pounds more than a ps 7.3. add on the bigger gas tank and the extra 2 feet of bed space that you have it will add up.there is a 4 cylinder cummins that will net you that though.same thing as the 6bt just 2 less cylinders

i agree with the 6bt as a better option but i have seen a guy running a 4bt in his superduty for mpg and he still tows with it but towing is the only time he reallyfeels a minor lack in power.he says hes getting anywhere from 25 and up which is your goal mpg wise so thats the only reason i suggested it.i myself decided to go with th 6bt though because the power/mpg plus i plan to mod mine to about 500 hp or so

i think its easily attainable with that setup considering you keep your foot out of it.most guys ive talked to say they average about 18-20 regularly just cruising around.it will be hard though cause the low end grunt the cummins makes.are you doing the swap yourself or having it installed at a shop?