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You can buy a 2017 Duramax 2wd and hope to get 16 mpg on the highway. But I suspect you like yours better. Good job.
 

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Sometimes it's better to stick with the Devil you know rather the Devil you don't know.

16 MPG highway, I'd park it or Cummins swap....o_O
I had to get rid of the 2018 g56 for an auto last summer for full time RVing, since my wife doesn’t do manual. That one for 22-23 highway. Not bad for a 4x4 on 35’s. This one drives really nice, but it loves the taste of diesel.
 

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OP. Great mileage. (y) Well done for that speed.
I've never gotten close to those numbers.
For now I'm used to my all around eighteen mpg.
I had a 1996 2 wheel drive that could get 26.5 mpg all day if I did 64 mph. When I hit 70, not only did the truck get much louder but it also suck more fuel. That was my only Cummins auto. My 12 valve manuals would only get 22 mpg at best.
 
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The early 2003 250-HP engines are better for top MPG when solo (some were NV-4500, had to have NV-5600).

But, loaded and/or towing the 305/555 engine has the overall advantage. The power bump is really the fine-tune HPCR got after field reports made clear that the sweet spot needed help (my belief).

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The nv 5600 and nv 4500 have almost the same OD ratio. .73 and .75. I think the auto would deliver better mpg with a .69 OD.
 
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True with 6.7L & 68RFE

The ’03 power problem made closer shifts better. And, can’t really tow in OD.
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I thought we were talking empty driving, I don’t think you tow anything ever with the 47re. 😆
 
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Matt, those number are nuts. I tracked mpg in my G56 for 6 months and best I ever saw was 17.8.

Then again, you had a hemi 1/2 tonner as well that could get 22-24 mpg 🥤
I’ve had so many trucks and seen so many different mpg averages. My 2014 1500 would get 26 mpg at 70, and my 2016 1500 would get 18.5 at 70. Figure that one out.

My 2013 g56 would get 21.4 mpg, at best stock at 70 and 23 mpg, at best deleted. My 2018 had a lot of work done, fixed blade turbo and all. It did alright if you kept off the throttle.

But I have never had a Cummins that got as bad mpg as this Duramax.
 
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I bought the entire package. I wanted to upgrade my gauges from a 1st generation Edge. The MM3 DD was a nice upgrade. I didn't have a tune switch on EFI Live. I sprung for the switch on the fly option on MM3 as well.

EFI Live box is pretty much a paper weight if one changes tuners. MM3 is much, much faster processor and upgrade all the way around.
I liked the mm3 on my 2013
 

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I'd forgotten all about the pesky drag :rolleyes: Seems from your comments then, that the MPGs effect of a 15-20 degree swing in ambient temp in Flatistan's Gulf Coast is likely negligible in steady-state cruising.
On a side, but related note; I will report that thanks to you guyz I spent $70 bucks on that black "air dam" contraption under the front bumper that was missing in my truck! But I'll make my money back in MPG savings right?... Right?... (1,000,000 miles later). Truth is I disliked how it looked without it. :cool:
I could probably stare at this for about a hour and a half and not get bored..



Tire Automotive parking light Car Wheel Automotive side marker light
 

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I put a set of the Michelin LTX A/T2 on my 06 I lost approx. 2 mpg over factory Michelin A/T tires, those tires have more traction then factory A/T tires, I wish I had waited the extra 2 weeks for the LTX M/S2...
Could have been the new squishy tread also that contributed, not just tread design. Give it some time to break in.
 
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WELL, NOW you got me looking at my Toyo's and they are showing some wear after only 25K miles. :confused:

Next tires may not be Toyo's, maybe M500s. I'm open and not married to Toyo's. This is my first set of H/T. They always seemed to have soft side walls.

The Bridgestone Duravis R500 HD Radial looks like a long lasting tire. If I picked 1 MPG that would be a home run!

That might be a year or 2 from now at the rate I'm driving these days.

Devil is in the details for sure.
I have the nitto dura grappler highway terrain 285/70 on 17” steel wheels for the Silverado. Supposed to be more fuel efficient. Doesn’t seem to be. So for fun I put some 35” (285/75) tires on the 18” wheels and I think my mpg went up.
I don’t have any real data, but the computer thingy is reading higher now. I’ll keep tracking it, see how good/bad it is.

Automotive parking light Automotive side marker light Wheel Tire Land vehicle

Wheel Tire Car Vehicle Sky
 
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Aero resistance with square wheelwells is killin’ ya.

(Captain Obvious says correct the computer for tire revs per mile; tire height).

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Yes I know, but it would actually read less miles than I am driving and therefore read less mpg than I am getting. So currently I am traveling 8% farther than it thinks and so my reading of 20.8, is probably more like 75 mpg. Right?
 
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