I have a 2002 2500HD with the 6.0L engine and 4.10's. I am looking at getting a new 1500 with the 5.3L because of gas. I get about 12.5mpg and it is getting really old. My buddy with the 5.3L is getting between 18 and 20mpg.
Is there any tried and true mods I can do to increase my mileage? ...or am i just better off getting a smaller truck? I know everyone says their mod will get you 15mpg, but the problem there is you have to throw money at the problem with out knowing if the cure will even hold up? I dont really want to do that. I hope someone out there has already solved this problem and can tell me what I need to do from the get-go to get the results I want. (better mileage)
THANKS!!!

 

Running synthetic engine oil will help some but you will still be way short of what a 5.3L engine will get. My 2005 Silverado Crew Cab 4X4 will easily get 18 mpg.

 

Hey rtreads, I know what you are talking about. I just bought a '02 2500HD with the 6.0 and I am getting maybe 13-14 on the highway. I knew when I bought it the gas mileage would be bad, but my buddies Hemi has more power and still gets 18 on the highway. I am going to a cold air intake and exhaust ans see if that helps.

 

rtreads, I just bought an '06 2500HD with the 6.0L and 4.10 gears. I'm having the same regrets
and asking the same questions, but besides driving conservatively and keeping it tuned up, there's not much you can do about mileage. 87 octane is about $3/gal and going up. On my best day, I get 14-15 MPG tops without hauling anything. I would consider buying/trading for a 5.3L. I like the truck, so far, but if I had to do it again, I would have looked around for a smaller engine in the same chassis. Not for the casual user who does not need to tow a trailer.
Let us know what you decide to do...