6.4l terrible mpg

pjtj2k · Aug 1, 2022

Ratman6161 said:
What are you to2ing when you get 11 MPG? I've also got the 6.4 + 4.10 and pulling my 7600 pounds loaded travel trailer I'm lucky to get 8. I once got 9.6 with a strong tailwind and less than 7 in hilly areas or with headwinds. I'm not complaining though. I knew what I was getting when I saved $9500 compared to diesel and $1 a gallon lower fuel price :;

I totally cheat when I'm towing. I cruise around 65 and get behind a semi to take the wind off me .
I'm towing Imagine 2600RB it's around 6500-6800.

dhay13 · Aug 1, 2022

pjtj2k said:
I totally cheat when I'm towing. I cruise around 65 and get behind a semi to take the wind off me .
I'm towing Imagine 2600RB it's around 6500-6800.

My son has a 2670MK. It weighed 8100lbs loaded up and advertised dry weight was 6600lbs. Had 1000lbs tongue weight. Towed it with my 2013 1500 Ram 3.55's then he towed it over 9000 miles with his 2018 2500 6.4 4.10's and has now towed it a few times with his 2021 2500 Cummins

Fatbob Frank · Aug 2, 2022

RacerRon said:
I also have a 2021 2500 6.4. My mileage started improving substantially once I hit 20,000 miles. Is currently sitting at almost 17 average with mixed driving. Idle time will murder the average fast. Stop lights and drive through lines kill it.

I only have around 14K on mine but I notice it's better this summer than last summer when it was relatively new...

Riccochet · Aug 2, 2022

dhay13 said:
My son has a 2670MK. It weighed 8100lbs loaded up and advertised dry weight was 6600lbs. Had 1000lbs tongue weight. Towed it with my 2013 1500 Ram 3.55's then he towed it over 9000 miles with his 2018 2500 6.4 4.10's and has now towed it a few times with his 2021 2500 Cummins

Dry weights, or UVW, are never accurate. They're simply a "starting point" for a given trailer model with no options.

dhay13 · Aug 2, 2022

Riccochet said:
Dry weights, or UVW, are never accurate. They're simply a "starting point" for a given trailer model with no options.

Yep. That's what I was trying to point out. Advertised tongue weight was 695lbs. Actual was 1000lbs loaded

Grimlock · Aug 5, 2022

I’m wondering is someone said they bought a Prius and it wouldn’t go over 20mph people would say well…ya don’t buy a Prius for speed. I’m not expecting the truck to get great mileage I’m expecting it to get what it should get. The issue is no one seems to know what that is. The truck is unloaded, 35s, at 70mph at fixed throttle no load it’s saying 10mpg. Even around town when it’s slightly better as soon as you touch the gas it drops to 6mpg. I mean I’m not flooring it I’m gently pressing it to pick up some speed. I can see tires size and weight having some effect but if for instance a similar 2500 under the same conditions gets 14mpg than something is up. I bought it used with the 35s on it so do not know if it has been recalibrated but again I can’t see that making a 40% difference.
Under normal driving mixed highway and street driving easy and thoughtfully it’s averaging 10-11mpg yes a lot of the time it’s reading way higher and sometimes way lower but it averages out at about 10-11. I fill the tank and get about 270 miles out of it.

retired · Aug 5, 2022

Grimlock said:
I’m wondering is someone said they bought a Prius and it wouldn’t go over 20mph people would say well…ya don’t buy a Prius for speed. I’m not expecting the truck to get great mileage I’m expecting it to get what it should get. The issue is no one seems to know what that is. The truck is unloaded, 35s, at 70mph at fixed throttle no load it’s saying 10mpg. Even around town when it’s slightly better as soon as you touch the gas it drops to 6mpg. I mean I’m not flooring it I’m gently pressing it to pick up some speed. I can see tires size and weight having some effect but if for instance a similar 2500 under the same conditions gets 14mpg than something is up. I bought it used with the 35s on it so do not know if it has been recalibrated but again I can’t see that making a 40% difference.
Under normal driving mixed highway and street driving easy and thoughtfully it’s averaging 10-11mpg yes a lot of the time it’s reading way higher and sometimes way lower but it averages out at about 10-11. I fill the tank and get about 270 miles out of it.

simple way to find out if it is calibrated is to get a stand alone gps or use your smart phone to down load a speedometer app. go out and set the cruise at 70mph and see if the gps or speedometer app matches.

Riccochet · Aug 6, 2022

Grimlock said:
I’m wondering is someone said they bought a Prius and it wouldn’t go over 20mph people would say well…ya don’t buy a Prius for speed. I’m not expecting the truck to get great mileage I’m expecting it to get what it should get. The issue is no one seems to know what that is. The truck is unloaded, 35s, at 70mph at fixed throttle no load it’s saying 10mpg. Even around town when it’s slightly better as soon as you touch the gas it drops to 6mpg. I mean I’m not flooring it I’m gently pressing it to pick up some speed. I can see tires size and weight having some effect but if for instance a similar 2500 under the same conditions gets 14mpg than something is up. I bought it used with the 35s on it so do not know if it has been recalibrated but again I can’t see that making a 40% difference.
Under normal driving mixed highway and street driving easy and thoughtfully it’s averaging 10-11mpg yes a lot of the time it’s reading way higher and sometimes way lower but it averages out at about 10-11. I fill the tank and get about 270 miles out of it.

You're running 35's on an already poor choice for fuel economy. I can't tell, but it looks like aftermarket wheels as well. All that rotational mass requires power to make it spin, power is made with fuel and air. Plus add in the additional rolling resistance.

Case in point. I put wheels and 35's on my 2012 JK Rubicon. Stock it was getting 18-19 mpg on the highway...now it's lucky to get 14 on the highway. Around town in stop'n'go it's like 10-11.

Go back to stock wheels and tires, see how much a little unsprung weight reduction effects fuel economy.

Irishthreeper · Aug 6, 2022

I just finished a 7,600 mile trip with our 2500 6.4 w/4.10’s, pulling about 10,600 lbs of 5W. I don’t know if it was the 89 I put in when it was affordable or crossing over 25k miles on it and more “broken in”, but my mpg took a nice jump. On flatter roads towing I was consistently getting 10 mpg and on a non towing trip the other day I got almost 23 at 65 mph. When Ive hand calculated the EVIC has averaged .4 mpg less than actual. I can’t help but think it’s the engine breaking in but also running the 89 octane. It’s boring to sit at 65 mph with CC on but there apparently big benefits.

dhay13 · Aug 6, 2022

Irishthreeper said:
I just finished a 7,600 mile trip with our 2500 6.4 w/4.10’s, pulling about 10,600 lbs of 5W. I don’t know if it was the 89 I put in when it was affordable or crossing over 25k miles on it and more “broken in”, but my mpg took a nice jump. On flatter roads towing I was consistently getting 10 mpg and on a non towing trip the other day I got almost 23 at 65 mph. When Ive hand calculated the EVIC has averaged .4 mpg less than actual. I can’t help but think it’s the engine breaking in but also running the 89 octane. It’s boring to sit at 65 mph with CC on but there apparently big benefits.

hmm. I have just under 27,000 on mine, albeit a 2018 6 spd, but the best I can get on the highway is just under 17 hand calculated but that's probably closer to 70 MPH. I have 4.10's also

Irishthreeper · Aug 7, 2022

dhay13 said:
hmm. I have just under 27,000 on mine, albeit a 2018 6 spd, but the best I can get on the highway is just under 17 hand calculated but that's probably closer to 70 MPH. I have 4.10's also

70 and above seems to be the trigger for me with mpg, it drops pretty fast. I mentioned above my EVIC shows low but I meant it reads high…usually about .4-.5 too optimistic. The nearly 23 I got was on flat roads, CC at 65 and letting MDS run. I’m wondering too if my tires are playing a role. Tread is down to about 1/3 left with all the towing and maybe that’s providing less resistance? I’ve been happy with the factory Firestones and will probably put the same tire on soon.

dhay13 · Aug 7, 2022

Irishthreeper said:
70 and above seems to be the trigger for me with mpg, it drops pretty fast. I mentioned above my EVIC shows low but I meant it reads high…usually about .4-.5 too optimistic. The nearly 23 I got was on flat roads, CC at 65 and letting MDS run. I’m wondering too if my tires are playing a role. Tread is down to about 1/3 left with all the towing and maybe that’s providing less resistance? I’ve been happy with the factory Firestones and will probably put the same tire on soon.

Yeah I still have the factory Firestones but maybe 30% tread too. I don't use MDS. I put it in 6th manually. Will have to try it at 60-65 and see what I get.
I have a spreadsheet with my fill-ups and miles and mine is about .5-.7 higher than hand calculated. A few have actually been lower than hand calculated

Irishthreeper · Aug 7, 2022

dhay13 said:
Yeah I still have the factory Firestones but maybe 30% tread too. I don't use MDS. I put it in 6th manually. Will have to try it at 60-65 and see what I get.
I have a spreadsheet with my fill-ups and miles and mine is about .5-.7 higher than hand calculated. A few have actually been lower than hand calculated

Let me know how it works out. I always value your opinions on here!

Riccochet · Aug 7, 2022

My Firestones are almost worn out. I don't like them in the rain either. Probably going Michelin LTX A/T2's for my next set.

06 Dodge · Aug 8, 2022

Riccochet said:
My Firestones are almost worn out. I don't like them in the rain either. Probably going Michelin LTX A/T2's for my next set.

I put a set of the Defender A/T2 on my 06 2500 and lost 1.5 mpg, I should have waited for the Defender LTX MS..

OC455 · Aug 11, 2022

Okay, recent Thruway trip....my house to Dr.'s office was 44 miles one way averaging 70 MPH. Didn't really pay attention on the way out what EVIC said mileage was. On the way back I took a look see on the EVIC mileage....it went up to 15.8-15.9 MPG (it was back and forth between these two numbers). Again averaging 70 MPH. The odometer is just over 20k miles now. Still running 89 for gas. I haven't filled up yet as I'm just below a half tank of fuel left and will wait until payday to do that and see if hand calculated is still a few tenths lower than the EVIC mileage.

I'm running Firestone Destination XT's on mine and they are awesome tires.

OC455 · Aug 18, 2022

Ok, just filled up the dually....

Went 379.3 miles and filled up with 27.28 gallons of 89 octane.

13.90 MPG is the average. Not too terrible for a big heavy gasser.

4xdad · Aug 18, 2022

My truck recently got 14 mpg on the highway at 70mph 35s magna flo d fit muffler resonator delete pulsar tuner to change the tire size and shut off the mds i still run the stock tune that is on the pulsar plus I put it on a diet it gained about half a ton with the rock sliders and tire carrier and topper with the lift like everyone else with ape I didn’t buy it for the mpg

4xdad · Aug 18, 2022

I hate spellcheck

JerryETX · Sep 26, 2022

Irishthreeper said:
I mentioned above my EVIC shows low but I meant it reads high…usually about .4-.5 too optimistic.

I don't use that app like dhay13 does (which is awesome info) but I do hand calculate my mpg about every other tank. In the year I've owned my truck it's never been close at calculating mpg. I recently went on a highway only trip and kept my speed around 70-73. No hills, no wind to speak of either way. Went 383 miles. Dash read 17.7 mpg. Actual was 15.43. That pretty normal for my truck and my experience with Ram trucks in general. City driving it's get's a little closer but the closest I've seen it is within 1.5 mpg. This is my 4th Ram truck. The last 3 have had computer calculated mpg and they've all been this way if not worse. My 05 with the 5.9 Cummings would read 22 mpg highway with actual being closer to 18.

6.4l terrible mpg

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