I wish I would have seen this thread earlier and set things straight much quicker...as I have alot of data from my 06 cummins truck.

The dodge probably said that it was getting 24mpg on the overhead display. It was not and was likely getting a hand computed 17-18mpg. I had a modded 06 cummins cc 4x4 and saw a very best of 18.7 mpg even though the display regularly told me that I was getting 23-25mpg. The overhead display is called a "lie-o-meter" on the cummins forums for a reason.

Keep in mind that diesel fuel is about 15% more expensive than gas so even my 2011 xtd cab 4x4 with the 6.2 is more economical to drive than my old cummins.

Some of the older cummins (2002 and older) can regularly get 20+ mpg on the highway, but would you like to be stuck driving an older cummins with all of 165 to 235 horsepower.

 

6.0 yes... AWD? No. And i have 3:73's

 

25? Sorry, not gonna happen...An LLY Duramax is lucky to get over 19 on the hwy at 70...stock or tuned.

And 24-25 in the common rail Dodge Cummins?...No way.

If anyone is getting 20mpg+ with a Silverado in any configuration, you're doing better than 99.9% of the people out there. I have never personally seen ANY gas Silvy get over 20hwy in my life...And I've ridden in/owned dozens over the years.

 

 

Gotcha! well here are some ideas.

TBSS or 08+ intake and matching TB
3.42 or higher ratio since its a highway warrior.
full tune up
smaller lighter wheel/tires. General makes a grabber highway tire that is low rolling resistance and standard equipment on basemodel 17's
headers with hi-flow cats
MIT or MIT JR kit
tonneau cover
weight reduction
maybe a good seafoam or engine cleaner. Also a good fuel injection service like from dealer or Kwik Kar.
Updated custom tune.

remember alot of little things add up quickly. Good luck

 

I've recorded up to 25mpgs on freeway @65mph.
6.2L 6spd CCSB, CAI,Muff,Tune 245/70/17 LRR tires, Tonneau cover, and very light foot.

 

wanna bet? my dad gets that on his 06 mega cab dodge ram I think hes seen better then that a few times.

 

Best I ever got stock with CAI and muffler in mine was 17, after a Wheatley 93 tune, going 65 with no A/C and perfectly flat road was 20.5mpg iirc.

20 highway isn't impossible, it is just highly unlikely in a stock truck. Tuned sure, but I don't see anyone averaging 20. La SS, you are one lucky guy, that is nuts!

 

So after the tune it will help mileage? Cuz that was on the way back from cali when i picked the truck up lol, Since then the truck is telling me i get 12.5 avg!!! ******* sucks

 

Yeah, a tune will definitely help! I picked up a few mpg in city and highway. You do have a 6.0, so don't expect to get what the 5.3's do.