I have an 06'4x4 lbz crew w/ auto trans. w/36k miles that currently get 14.5 city/mpg. It currently has zero engine mods and is basically a blank canvas for upgrades. I am mostly interested in gaining mpg's as the increased power will come from the tuner,intake, exhaust, etc. So, my question is for anyone out there with experience, which upgrades focus on economy? I read about several people in diesel power mag getting 20+mpg. How can I? Would downsizing from 20in. wheels to 18in. help? Thanks!  

bigger tires = more rolling mass, heavier wheel tire combo too. question is did you change the gearing in your truck when you did the bigger wheels/tires? you may have the wrong gearing.  

For better mileage, I would suggest a turboback exhaust, PPE tuner, cold air intake from Banks and a set of gauges (boost & pyro) to monitor everything.  As for the wheel/tire combo you have, if they are the same overall diamater as stock, then they have -0- effect on fuel mileage.  

I haven't even thought about the gear ratio!... I'm not sure what ratio I have, all I know is that its completely stock. That's a great suggestion. My wheel/tire combo isn't very heavy, the tires are 305-50-20 and the wheels are 20x9 Diamo 17 Karat. I just thought maybe going with 18" wheels and tires that aren't so wide might help with the economy. And what about the oil, has anyone tried Royal Purple or Rotella? Does it really make that much of a difference? Thanks for the reply!  

The diesel shop I've been talking with has suggested some kind of "in-house" turbo back exhaust that they say is comparable to MBRP...? I have also researched PPE tuners for their ability to eliminate trouble codes, which I hear can be caused by installing turbo back exhaust...? Is this correct? Is the PPE Hot or Hot+2 better than the Economy Tuner for mpg's? Also, I have looked at several cold air intake systems and can't decide which is really better, there always seems to be a give and take between manufacturers. What about the good, old fashioned K&N Intake system? I know Banks is also tried and true, but what about Volant? They seem over-priced...? I appreciate the feedback before I invest my money in the wrong products. Thanks!  

B.Akoneto, no matter what PPE you choose, the gain is what changes.  The hot and hot+2 just add more power choices over the standard.  The economy only has 3 power levels whereas the standard, hot and hot+2 have plenty more!  As for a CAI kit, S&B is highly ranked as far as performance per dollar!  The K&N is fine if you are careful to not overdo the oiling.  Most owners are leaving the stock airbox on as it flows enough air for 500hp.  The volant is another great intake, but very expensive for what you are getting.  Banks makes a ram-air kit, which works very well, but like all of his stuff, it is pricey.

Hope this helps!  

in-house exhaust is more then likely alot cheaper then the name brands, as for intake aem, afe, s&b are the tops for diesels ive seen alot of diesels that have sand and other objects in the turbos thanks to k&n. the ppe econ is set for better mpg, lower hp, compared to the hot or hot+2. as for banks im sick of thier stuff just cause they add some power without making your truck smoke doesnt mean anything, you can get more power for less with other products.  

as for the wheels/tires they are bigger and wider then the stock ones, and yes they are heavier to so its causeing your truck to work harder to turn the wheels.  

needpower, he never said what size rims or tires he had.  If his stock size was 265-75-16 and he went to a 265-35-20, its the same width and overall diameter as the stock setup.  Just because you increase rim diameter, does not mean you have increased overall diameter.  Now if he was running a 315-50-20 then yeah, thats why the fuel mileage sucks.  But if OD and rim width is the same, there is -0- effect.  

"My wheel/tire combo isn't very heavy, the tires are 305-50-20 and the wheels are 20x9 Diamo 17 Karat. I just thought maybe going with 18" wheels and tires that aren't so wide might help with the economy." actually he did, not to be an ass but read something before you call me out on it.  

and also heavier wheel/tire combo effects mpg too not just overall size  

Just read the first post when I wrote that, my bad.  I take it all back, you are right in all regards.  Perhaps going back to a stock size would give him the MPG numbers he seeks.