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All things equal, how much are MPGs influenced by ambient temperature? I understand there are a ton of variables and other factors also described in @steve05ram360 various posts, but if you were to take a ballpark guess, would you say 20 degrees make a difference? This morning I ran 300 miles round trip, mostly cruise control @70 (2050 RPMs or so, 4.10 diff), and I seemed to have gotten a 1 mpg difference between the legs. 18 vs 17 mpg. Only material difference was temp at 70F when I left at 6 AM and 85 F when I returned around noon. I know it is too short of a trip to really put too much weight on it, but since turbos like cooler denser air, I figure there is some impact. Or is the difference inmaterial unloaded at those RPMs making 7-8 PSI of boost with EGTs between 7-8k?

PS: Pardon if this has been already discussed but could not find a reference after limited searching
 

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06 3500 Mega 4x4 DRW
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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:
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06 3500 Mega 4x4 DRW
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I might take off my side bars and rear mud flaps on my next trip to IL. They look like more stuff producing drag.

I just replace my tonneau cover. It was 13 years old and had over 200K on it. Folks say this cover helps with MPG. I like to think so too and like to have my contents covered...
Thank you sir. All 4 flaps on mine are new. Hate the thought of every rock and piece of debris chipping away at the paint. Tonneau cover is on my list but starting with injectors, I have about $8k of "needs" ahead of it so it may be a few... hmmm... years! :D
 

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06 3500 Mega 4x4 DRW
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I might be crazy, but I think you have 3.73s. I’m pretty sure 4.10s run much higher at 70.
You (and others) certainly know more about this than diesel truck rookie me. I am going by the factory Build Sheet "Equipment Listing" based on the VIN. See the particular section below. Everything else in the Build List matches. Also, every time I see peeps posting about speeds and tachs, it seems they always turn less RPMs than me. But I guess it is possible the original 4.10s were replaced. She did come with the taller than stock Falken 285/70/17 Rubitreks which should account for about a 2 mph offsetting difference @70. In any case, I would love to confirm from others that run 4.10s. If I do have 3.73s then ****... my MPGs really SUCK! :oops:
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06 3500 Mega 4x4 DRW
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I might be crazy, but I think you have 3.73s. I’m pretty sure 4.10s run much higher at 70.
Woke up thinking about this, and I ended up here: http://www.grimmjeeper.com/gears.html

Punched-in the numbers & the results seem to match 4.10s best. My tach may be around 100 revs lazy @70, while 100 revs over @75. Maybe at higher speeds the Mega DRW w/AT tires has all sorts of drag of drag, inducing more tire slip, making it show more revs than would be expected with the 4.10? Still 5-7% error range on a 16 yo tach-needle known to be "less than perfect". Speed is from GPS so I don't question that one.
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06 3500 Mega 4x4 DRW
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Made it to PA from the PROF (People's Republic of Florida). My best mileage was 16.9 MPGs over a 530 mile segment with cruise set at 67 mph (3-under speed limit) with the 5.9 turning roughly 2k RPMs. Empty, A/C on, EFI Live 1, and running 60/40 PSI (cold) front/DRW respectively in the relatively big 285/70/17 ATs.

Disappointed as I was hoping for at lest 18-19. But as I get slapped back into reality, I have to recognize that the following is costing me probably around 2-3 MPGs?
  1. 4.10 Diff
  2. Bigger draggier heavier tires
  3. Misbehaving injectors 4 & 6
  4. Unknown EFI Live tune
  5. Play in steering box
The steering box's play is not enormous but that 1" or so at the steering wheel causes a ton more diesel-sucking corrections regardless of how hard I try. On a related subject, I also noticed that RAMsey seems to be particularly sensitive to "lean" of the highway. Some lanes in many highways are tilted X degrees for water drainage. In these instances, my wheel would be compensating at the tone of ~30+ degrees which must add a ton of drag.

For my trip back I intend to add 5 PSI to all 6 Falkens & run EFI Live 2 which wakes her up a little. If I can source enough psychological and emotional strength, I will try a tank at 65 MPH...
 

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06 3500 Mega 4x4 DRW
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Thanks guyz. U r lifting my spirits a bit....

I have the S&B Cold Air. I could loosen the top clear acrylic cover screws and run it with it popped open to suck warmer air. Will try that indeed.

On the LOM subject: I seem to have the craziest of them all. I read LOMs being off single digits, but my crazy-ass LOM is consistently 100% over. During that 16.9 mpg run, I think it actually showed 33. And throughout the trip, it was literally close to double, almost always. My taller tires seem to only affect the speedo about a 1.5-2.0% (under-actual) which should not be what throwing it off.
 

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06 3500 Mega 4x4 DRW
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IMO, need to get RPM below 1900.

Also, at 67-68/MPH one is having to get into the left lane to go around 65-MPH commercial traffic.

Also, in aerodynamic terms, one is past the last gate to FE.

Also, the travel time difference between 64-MPH and 68 is negligible. It will not equal 4-MPH average.

— Engage cruise control at 64-MPH as you’re coming down the entrance ramp (given vehicle spacing). Don’t turn it off till you’re exiting the road.

— As above you have the worst mechanical spec for FE (but best for hard work). The operator has to adapt to the vehicle.

Look at this way: “Man, I’m on vacation running solo at 10-11,000-lbs versus being hooked and grossing 32k”.

Steering (and tire design) are killing what the truck can do. It’s cheap/easy to add bushings to the steering column shaft near floorboard (search threads). And it sounds like the alignment needs a check. Tire rotation and — if over 40K — consider new shocks (Bilstein 5100 equivalent).

Soon after some TLC — and the driver has become accustomed to doing road trips differently than beforethe two of y’all will settle in together as the check list first grows then diminishes in length as questions are eliminated.

What was important to FE didn’t matter before. Now, it does.

The majority of slack (between received against what’s possible) is the driver.

It’s not easy to do both truck & driver at the same time until you get used to it!!

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Thanks. All great points well-taken. I will try 64-65 MPH on my way back. But man, rarely do I see a rig below 67-75 in I95 unless they are a tanker or heavily loaded.

My truck actually tracks VERY well on a leveled road, and there are no vibrations. Alignment and balancing recently done. Steering play is 99% the factory-looking box. I also have '09 steering upgrades, etc. A new box is really needed, new better shocks are indeed in the near future, and to @Alcharger's point, urethane upgrades in key points seem to be well worth it.
 
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Given as I have thousands of miles on IH95 from near Miami to near NYC at 62-68/mph the past dozen years, I’ll dispute that part.

Truck traffic hovers near 65. Big trucks and cars have little awareness of each other as groups.

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Fair enough. I will make an effort to roughly count how many blow past me... Perhaps not the majority, but a fair share will. Surely is also a function of time of day as well...
 
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06 3500 Mega 4x4 DRW
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06 3500 Mega 4x4 DRW
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To formally update: back in FL after 1,300 miles.
  • This time I took the I-81 to I-77 "western route" to take a break from I-95 madness. Certainly super nice scenic route through the mountains. I was able to score a 17.1 MPG in that first tank through lots of arguably steep climbs. Also about 1 hour of backroads driving initially in the trip. I suspect there may have been a net altitude gain of probably 500-1,000+ feet in elevation by the time I refueled in Charlotte, NC. Max 65 mph and always on cruise even though that may have hurt me more than helped up and down the mountains. Upped fronts +5 to 65 PSI cold, left DRWs at 40. RAMsey really liked the 65 up front. I think she has an 18 mpg in her with current tire package. Probably doable in flat land with that max 65 mph on true granny-mode as I was. And of course, with properly working injectors (see note 2 below).
  • Between Charlotte and Wildwood, FL I matched my previous best at 16.9 MPG. But in this leg, granny-mode malfunctioned a few times :cool:🤷‍♂️, and there were more unscheduled stops as it is now a known fact that my bladder simply cannot match RAMsey's range :sick:
A few side notes:
  1. While in PA, I discovered the new-to-'06 Tow Haul Mode (1 click on button). This locks the TC on 3rd which is sweet! So 3rd, lockout, then unlock to shift into 4th, and relock. I feel it has to improve MPGs. Plus it kept my tranny temps as low as I have ever seen. Seems like shift points are also adjusted to be a lot more sensitive to throttle position. The downshifts are a lot more aggressive (earlier), but that seldom happened at an unneeded time. I think this is a net gain rather than a downside when empty. For city driving I am now a fan of Tow Haul Mode (1 click).
  2. I had about a quart and 1/2 of ATF/2SO in that initial 34 gallons. I presume this will hurt efficiency a tiny bit. And yes, I still have misbehaving injectors :mad: (I'll update that thread once I run the AlfaOBD test).
  3. I ran the entire trip on EFI Live 2. Whatever that may be... I will likely test 3 next as positions 3 and 4 have the highest probability of being simply just plain'ole hotter tunes vs a tow or econ tune. Seems 1, 2, and 5 are the likely spots for econ and tow map positions.
 
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2nd TC lock will be even sweeter. And higher pressures are going to make my shifts even better as well. Looking forward to Rob's tunes as most likely there is at least 1-2 mpg to be had in a few of his tunes as well from what I have read. I have been trying to hold off until I either cure or capitulate on injectors. But I will likely end up getting the MM3 package well before then though...

Speaking of the devil LOM; I seem to have the most insane of them all. It appears most of you guyz have it up to 50% or so over actual. RAMsey's LOM is almost always a solid 100% over (2x)!!! Crazy talk... I ended my 17.1 MPG run with a reading of 36 mpg on the LOM. The 16.9 tank showed 34.8. :rolleyes:
 

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06 3500 Mega 4x4 DRW
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I just ordered HDF. I'll try it my trip to N Ga mountains next week and report back.
You beat me to it because at the website I found MEANER POWER KLEANER - Advanced IDX4® Diesel Detergent | Howes Products . So now I am wondering if this is a better option for more concentrated injector cleaning focus. I wish they (anyone) made something specific for pre-emissions common rail injectors as I am sure there all sorts of limitations when formulating a product to be marketed across many mass-produced diesel platforms and generations.
 
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Run an extra-strong dose (each). Together. There’s a synergistic effect in my experience.
View attachment 957490

View attachment 957491

Then switch over to HOWES MEANER CLEANER.


And stay with Defender afterwards.

There’s probably stronger. Never hurts to find and use STANADYNE.

— Just be aware there’s some random steel can formulations in farm country I don’t think I’d run in a road diesel.

The above will get tank & injector (tips & bodies) about as clean as OTC will deliver.

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Alright... I am going to follow your advice. My injector resurrection hopium is fading fast. I'll update in my related thread: AlfaOBD Cylinder Performance Test, Fuel Pressure... . I intend to do a new Cylinder Contribution Test tomorrow to see changes after this last trip, and use the new numbers as reference point for your suggested treatment plan. Thank you!
 

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06 3500 Mega 4x4 DRW
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The advice about towing heavy and keeping EGT high (above 1,000-F ?) for a few hours likely the best accompaniment to the above.
I agree and have not had the opportunity to do so (I sold my boat :( ). But EGT is one of the reasons I took the western route. Even though empty, at least I got to lay on the EGTs a bit harder and more often when climbing. I did manage 1-1.2k for sustained minutes here and there. And I had enough ATF/TCW3 to clean the entire state of Texas.
 
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