Title pretty much sums it up witch is best on fuel economy? I know the 6.7 needs a dpf delete to be even close, but with light mods what kind of mpg numbers are realistic out of each. Keep in mind I'm not lookin for massive power gains, just for a good daily driver..

 

6 speed 5.9 cr. should get u atleast 22 with a mild programmer, intake and exhaust and keeping ur foot out of it

 

I have an '04 5.9 CR 6 spd and get about 18-19/gal....a buddy has an 07 6.7 6spd w/ DPF delete and Edge Juice and gets around 15....we seem to have similar driving styles(gettin on it every now and then)...The only real difference in our trucks is his tires are about 1" taller.

 

i get over 20 with stock tires

 

Im gonna have to say a 6 speed 5.9 especially an 03 and early 04.

 

If I was comparing the 2007 5.9L and a 2010 6.7L with the full SCR it might be closer than you think. On the otherhand any 6.7L without the full SCR is JUNK... Get a 2004.5 5.9L and have fun.

 

I am getting right at 16-16.5 on my 5.9cr 6 speed. But it only has 14,000 miles on the engine so I guess it will get better with time.

 

My 5.9L w/ G56 (AE ratio) only averaged 1 mpg better than my 6.7L.
(17.5 vs. 16.5). I put 44,000 miles on the 5.9, I only have 9,000 miles on the 6.7.

 

5.9 all the way

 

Thanks for your input guys I'm goin to sign papers on an 04 quad cab 4x4 auto. I know man. Trans would have been better but the wife is gonna have to drive this one... So it has to be auto or I'd be replacing clutches and transmisions every month.. Lol!