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I can't contribute to the 3/4 ton and above or 4th gen but my 06 1500 with leveling kit and 33's averaged around 11 MPG. I also ran 89 octane in it per owners manual as well. I am not sure with the new additions to the hemi over the years increase gas milage but mine was a contributing factor to getting a diesel, atleast thats what I told my wife
 

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I have a 13 Outdoorsman CCSB 4x4 w/ 2in level and 35's. Exhaust, Moe's 87mm, S&B intake, I get 10.5 around town. It's only 6 miles to work and the truck only has 9k on it. I did see 15 when I drove the interstate.
 

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I just got a custom tune from Sean at Hemifever, I don't have any mileage numbers yet due to the terrible weather here, in 4x4 all the time lately, I can tell you the mileage has not gone down being in 4x4. Anyone with a 5.7 needs to get a tuner from Matt at Moe's, then talk to Sean at Hemifever, it is a complete change in the truck. I am happy with the gas engine now.
 

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I just got a custom tune from Sean at Hemifever. I am happy with the gas engine now.
Which octane tune made you happy? I have a 6.4L and have been curious about the 87 octane tune (which may not be an option for the 5.7) but I don't know how better it will be than stock. I'm actually okay with the stock tune except for the MDS. The only thing I'd like extra is more low-end torque, at around cruising RPM. I figure if I have to tune it to get rid of the MDS and if any tune, even eliminating MDS, might affect my warranty, I might as well tune it to get more torque/hp too.
 

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I have the 91tune and I could not believe the untapped power these trucks have. The DCX does have the MDS disable, I don't have MDS. Sean has you record a run with the DCX doing different things like stop light to stop light, general crusing, and a 0-75 WOT. You then download it to him, he tweeks the numbers, resends you a custom tune per the numbers and the available octane in your area, gearing and so on, you load it and you are done. The DCX holds you OEM tune for when you have to go to the dealer for service
 

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tat2thor,
You've got me really considering a tuner for my 5.7L HD. Which, btw, I love. As for mpg, I avg high 12s/low 13s on my 12 mile drive to work. Not bad for a 4x4 2500 mega cab.
 

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Can we definitely say what engine gets better MPG?
I'm seriously thinking of going with a hemi in a new truck. The only one that matches the color/options I want is a 5.7 . MPG is important to me for the choice. Which one to get?? ?
 

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When my '07 was stock, I was getting 13mpg with it (3.73 gears). This was town and rural country roads here in the Appalachian Mtns. I have not calculated it since I put 34's on it...
 

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I know it's a little different, but I am really happy with the 5.7L in the wife's new jeep. For cost and simplicity it was a good move for us over the diesel option. Not sure what all the differences are between the motors in the trucks besides the HP rating. She drives about 50 miles a day with some highway and averages 19 - 21mpg. It does very well towing a 2500lb trailer. I filled it up Saturday and got 21.3mpg. The GT tuner does help with mileage on the 91 octane tune, but I really don't like how sensitive it makes the throttle. I have also heard good things about the hemifever tuning.
 

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I know it's a little different, but I am really happy with the 5.7L in the wife's new jeep. For cost and simplicity it was a good move for us over the diesel option. Not sure what all the differences are between the motors in the trucks besides the HP rating. She drives about 50 miles a day with some highway and averages 19 - 21mpg. It does very well towing a 2500lb trailer. I filled it up Saturday and got 21.3mpg. The GT tuner does help with mileage on the 91 octane tune, but I really don't like how sensitive it makes the throttle. I have also heard good things about the hemifever tuning.
Sean at Hemifever will hook you up. Best money I spent on a gas tuner. Customer Service is also fantastic. You will NOT be disappointed.
 
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Can we definitely say what engine gets better MPG?
I'm seriously thinking of going with a hemi in a new truck. The only one that matches the color/options I want is a 5.7 . MPG is important to me for the choice. Which one to get?? ?
If going gas, I'd get the 6.4 if possible. To me it seemed like there was a pretty noticeable difference in power between the 6.4 I test drove and our 5.7 work truck.

Work truck EVIC shows 14.5mpg but I have not hand calculated it. It usually runs around empty on base but we have had some back road 60mph long cruises. Those trips it usually has 2 people and ~300lbs of equipment.
 

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i have a 14 ram 2500 with the 5.7. I came from an 05 with the 5.9 and i do miss the torque but couldnt justify the almost 10k difference in price. As for fuel economy (unloaded) i dont see a whole pile difference.

I get 18.5 mpg hwy (imp gal)
my 5.9 i got 20 mpg hwy (imp gal)

Never checked driving around town but its not real pretty
 

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I test drove a 2012 5.7 2500 4x4 and a 2015 6.4 2500 4x4 today and didn't notice as much difference in power between the them. I thought the 6.4 would have a lot more power but they both felt strong. I would give a little edge to the 6.4 and I was having too much to pay attention to the MPG's:party018:
 

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If you can drive on a highway with any hills you will notice the difference. Our 5.7 at work hunts for gears more than the 6.4 I drove.
 

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I started to leave the truck in 5th gear around town and anytime below 55mph and my average went up some, doesn't "lug". I am not expecting good fuel mileage with a 3/4 ton with 35's.
 

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I have a 13 Outdoorsman CCSB 4x4 w/ 2in level and 35's. Exhaust, Moe's 87mm, S&B intake, I get 10.5 around town. It's only 6 miles to work and the truck only has 9k on it. I did see 15 when I drove the interstate.
Geeze, I get 1.5 mpg better than that pulling 10 k lbs @ 80 mph. Oh wait. I have the diesel. I thought we were on the Cummins Forum?
 

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Are you saying you get 15 us mpg towing 10k at 80mph?

If so please sir show me the pictures of pigs flying.
 
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Are you saying you get 15 us mpg towing 10k at 80mph?

If so please sir show me the pictures of pigs flying.
No. Can you read and add? 10.5 mpg +1.5 = 12 mpg. And yes, I am getting 12 mpg towing 10k at 80 mph.
 
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