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Old 09-18-2016, 06:57 PM   #1 (permalink)
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New to EcoModder, Ram 2500 diesel

Hey guys! I just bought this truck partially based on a few threads I read here on this forum; I wanted a full size truck that won't wreck me on bad fuel mileage, and it seems like a lot of people have had success with the Cummins engine. So I wound up with a 2003 Ram 2500 4x4 6 speed manual:



On the trip home, I got 16.4 MPG cruising at no more than 1900 RPMs (65 MPH)... Granted, this was through some very hilly country, and I had a motorcycle in the back. I would like to do whatever it takes to get myself consistently over 20 MPG, hopefully even as high as 25+ MPG on the highway. Everything on the truck is stock right now, so I'm really not sure where to begin, as far as what's going to give me the most immediate bang for my buck.

Any thoughts / ideas are welcome!

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Old 09-18-2016, 11:43 PM   #2 (permalink)
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To go from 16 to 20 its going to involve axle gear change.

Remove all the emissions control garbage. Since I don't think WY has a smog problem.
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Old 09-19-2016, 12:28 AM   #3 (permalink)
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Welcome Aboard

I used to work for Cummins... back during the introduction of the common rail injection system on that 5.9 of yours.

I love those engines... and although I own a Ram its not a diesel... but if I ever get my hands on one
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Old 09-19-2016, 08:20 AM   #4 (permalink)
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There are several of us who've posted with some detail on owning/operating early HPCR Cummins (3rd Gen).

FWIW, I can see 16-mpg pulling my 35' travel trailer. About 17,000-lbs as a combined rig.

4WD Dodge has a problematic front end. Slop. Then, the steering is also vague. Will be worth the time and money to R&R the whole thing. I'd recommend KONI FSD shock absorbers (Hendersons Lineup) as a start, along with polyurethane anti-roll bar bushings.

Verify, don't assume, ideal alignment, zero brake drag and no CAC system leaks.

Tire choice is worth 2-mpg on the annual average. I'd rather have commercial traction tires such as Bridgestone Duravis m700 versus the usual boy toy tires.

Front air dam low enough to be at lowest height of undercarriage protuberances (conveyor belting).

Do a search around here. Several trucks close to yours with good average numbers.

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Old 09-19-2016, 08:30 AM   #5 (permalink)
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That is pretty much exactly the truck I was thinking about getting as well, just the short bed version. Does your truck have the 3.7 or 4.1 ish gears? I got to say, I was under the impression they should get 20 mpg at a 65mph steady cruise all day.
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Old 09-19-2016, 11:08 AM   #6 (permalink)
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Have to keep them under 2,000-rpm to see 20+ consistently. The highway operating speed range is 58-63/mph for reasonable economy as well as for longevity.

Plus, the propensity of high COG pickups to roll over (where cars will skid sideways) as well as braking performance means 65-mph is "top speed". I hope -- that with this group atlround here -- that I don't to again go thru the travel speed versus average speed "problem". In shortest terms, there is no benefit to running fast. "Time saved" is about having the TV remote control in hand sooner.
Long term economical operation is about establishing best habits (consistent with safety).

4WD Dodge 2500/3500 of this era need the front steering and associated replaced with up to date design. Next is learning how to shift the 5600. Every gear, every time. It's a transmission from the medium duty truck lines (like the engine) thus shifts slowly.

At over 200k I'm on the original clutch, first brake re-line, and Michelin replaced the defective first set of replacement tires (only saw 70k versus the originals at 120k. Was on track to not need second replacement set until truck was at 250k).

A vehicle like this requires a fresh start. One does not "keep up with traffic". It's slow around town. It's meant to do a great deal of work with a long life at a low overall cost.

Tye engine is pretty much a 10,000-hr lifespan. That's figured at an average of 35-mph from engine hours versus miles.

OP, what's the average on yours. Engine hours divided into miles? (Personally, I wouldn't have bought one with an average of under 25. Mine was at 47. Previous beings owner apparently didn't stop except to buy more Diesel and cigarettes to have one that high).

A 350k mile engine life isn't likely without a correspondingly high average speed.

CumminsForum a good place to get a handle on mech issues. Smaller crowd at TDR, but exceptionally sharp.
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Old 09-19-2016, 12:36 PM   #7 (permalink)
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Quote:
Originally Posted by oil pan 4 View Post
To go from 16 to 20 its going to involve axle gear change.

Remove all the emissions control garbage. Since I don't think WY has a smog problem.
It's already 3.73, are there options available that are even lower? And yes, I can legally do anything I want with emissions / exhaust. Once I get into that, should I straight pipe it, or is the back pressure from the muffler at all important to maximum efficiency?

Also, responding to slowmover, thank you! However, I'm not sure how to check the engine hours. I have about 280k miles on the odometer.
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Old 09-19-2016, 01:00 PM   #8 (permalink)
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He said he did keep it under 2000 rpm.
My Hemi 4x4 (with 4.1 gears no less) gets over 18 mpg running 65 mph in the mountains of Western Montana.
See this is why I am hesitant to get the cummins. I see so many claims on the diesel pages but then when I drank the cool aid and bought a Duramax I never saw even 18 mpg empty or better then 12mpg with a big slide in camper. It was so bad around town both MPG and having a crew cab long bed that it sat most of the year unless we were using it on vacation. My Hemi is nice all year long although I still have kept my Forester and use it most days because I don't know if I will buy a 2500 pickup again. Ugh. Maybe I will ask the lot if I can take the Ram I am looking at for a whole day and do some MPG testing with it.
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Old 09-19-2016, 09:14 PM   #9 (permalink)
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Turbodiesels do not need "back pressure".
Chances are there are much numerically lower ratios available. I don't know what the dodge axles are.
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Old 09-19-2016, 10:43 PM   #10 (permalink)
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That's the truck of my dreams right there. The 2003-2004 had the common rail engine, but lacked the DPF, cat and all that other garbage. Good taste in both trucks and bikes (see my garage)!

I've got 3.54 gearing on my 1998.5 Cummins 4x4 and achieved 22 MPG at 65 MPH on my last trip. That's with an automatic tranny that is in terrible need of a rebuild, and a very sloppy front end that required 30 degrees of constant steering just to go straight. 1600 RPM is a good sweet spot for that motor, and I was probably at 2 or 3 PSI of boost the duration of the trip.

If you don't need the traction, get road tires. They will be much more fuel efficient and quieter.

I've had several brake calipers either seize or allow air into the lines. Don't know why the calipers are so problematic, so check them often.

Get a bed cover to improve aero. Agree with all the other suggestions on here. 20 MPG is doable, but you'll probably need a gearing change.

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