Found a 08 4X4 135,000 Miles, what are the differences in mileage and maintenance from the 06-07 5.9?
All comments welcome.

 

6.7 requires more maintenace due to emissions components. Unless you plan to delete, 5.9 would costs you less to maintain over time. Any repairs over 100K miles are on your dime. Emission components on 6.7 are very expensive to replace if they should fail. Injectors on 6.7 are three times the cost of a 5.9 injector. 5.9 will get better MPG because there is no DPF to regen. No O2 sensors, exhaust temp sensors, EGR valve, egr cooler and sensors that monitor all the emission components. Turbo on 5.9 less likely to fail because of soot buildup. Common problem on the 6.7 turbo nozzle seizing up due to soot buildup also turbo speed sensors high rate of failure at a cost of $300 to replace. No new turbo for replacement only remans. 5.9 would be less of a maintenace headache for sure. 6.7 CTD engine are bullet proof and the best truck on the market but only if you use this truck as designed, open road and tow vehicle. Not to be used as a grocery getter.

 

As a general rule the new 6.7's get worst mileage because of all the crap they tacked on and the DPF regeneration process eats up fuel as well. Many folks delete the 6.7's and swear by the results.
I started off looking to buy a 2012 to replace my 2004.5 but after a bit of research I decided for my around town driving style the old 5.9's would just be a lot less problematic. I lucked out and found a low mile 2007 G56. Now I can't bring myself to sell the 2004.5. The wife thinks I'm crazy to keep both. I keep telling her that the two I have were cheaper than a new 2012!!

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In stock form the 4th gens have become quite reliable off the lot, but milage is still crap compared to the 5.9s

Modded, the 6.7 becomes the 5.9s big brother that scares the crap outta people. Is crazy what they are capable of. Head gaskets may be trouble some for the foolish, and the only major short coming, on huge builds, are the connecting rods.

 

I had a 2003 a few years ago and loved the truck. It had a manual tranny and the fuel mileage was great. I was reluctant about buying my 2007.5 with the 6.7 but all I can say is wow. I can now get around 22mpg(hand calculated) on the highway with the smarty, cai, 5" tbe and with the original tire size still on the truck. The power out of the truck is night and day difference against my 03 with equal mods. Pulling my 8,000lb camper is so nice with the new 6 speed auto using the tow haul and the factory engine brake. I average around 2000 to 2500 miles a month for work on the truck and have only had one problem while still under warranty when the transmission cooler leaked inside the radiator at about 70,000 miles. I added the smarty at 88,000 miles. Either truck is a good choice but Im glad I didn't let some others bad experiences keep me away from my 6.7