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JustLuckey 04-30-2011 12:59 AM

Hello, I drive a big truck and I like efficiency
Hey folks, I'm glad I stumbled on to this site. It seems to be right up my alley. First, let me give some background on myself.
I'm 34, married, and have my first child (son) due in about a week. I live in Northeast PA, have a bachelor's degree, and am a project manager for an engineering firm.
My current vehicles are:
2005 Dodge Ram 2500 QC SB 4x4 w/5.9 Cummins (auto)
2008 Toyota Camry V6
I know, they aren't your typical eco-type vehicles, but let me continue...

I did have 2006.5 VW Jetta TDI. We loved the car, consistently got 42-45 mpg and put 115,000 miles on it in less than 4 years (we commute a lot). The turbo (actually, the wastegate) went on it (out of warranty) and the DSG tranny started to show signs of problems. With a pregnant wife and winter coming, we wanted a more reliable car. So enter, the Camry.

Anyhow, my truck is my focus for this site. The 3/4 ton rig, as you may know, doesn't have any EPA estimates on MPGs. From being a member on several forums and having a few friends with various models of Dodges with the 5.9 Cummins, I have seen City mpg range from 13-16 and hwy 16-20. A lot has to do with gearing (I have a 3.73 in mine), but the 4.10 is a fuel pig. When I first got my truck, I was seeing ~15-17 city and 18-20 hwy.

I'd done a few mods and am now seeing 18-20 city and 24-26 hwy. My goal is 30 mpgs on the highway, but we'll see. I still have a few mods to make. It's worth mentioning, that my numbers above come from hand calculation. As my OBC is very optimistic. On highway, when I'm doing the speed limit, it quite often reads 30-33 mpg (I wish).

My wife and I make several trips to GA every year. It's about a 850 mile trip. We've made it half way thru SC before fill up (750 miles or so). My next milestone is GA border (which is ~780 miles), then the 800 mile marker is the following milestone. Ultimately, getting to our destination without a fill-up would be awesome.

Here's my current list, in chronological order, if I recall.
5" Turbo back exhaust with free-flow (too loud though) muffler (RPM Outlet)
Solid fold tonneau cover (Extang)
Fuel Mgmt tuner (Quadzilla)
Larger intake manifold elbow (Banks)
K&N (larger than stock) filter
Michelin Low Rolling Resistance Tires (slightly taller/skinnier size than stock)
Bully Dog Triple Dog Gauge/tuner (normally set to stock tune)
I often run / rotate fuel additives (Power Service white or grey and Lucas diesel treatment.

I just got my flex-a-lite electric fan this week and hope to install it soon.
Future mods include:
Cab-high cap
Air dam to fit under bumper (this is a stock item that the previous owner removed)
More free flowing exhaust manifold (BD or aFe)
Manual Locking front hubs (Dynatrac or other)
Upgraded (more efficient) torque converter (Few option)
Larger, more free flowing intercooler (Banks)
2nd overdrive gear (article in diesel power mag)
At some point, a water/methanol injection kit (Snow Performance)

My goal has always to do efficiency upgrades without losing any feature or amenity (deleting the power steering, AC, or wipers are not options), to keep the look close to stock, and to keep it useful for what my intent for it is (hauling dirt, mulch, wood, towing, commuting long distances).

I'm open for other areas/ideas of improvement....with my list, I think the main issue is aerodynamics....which will be tough to keep a relatively stock look intact.

Anyhow, I thought I'd introduce myself. Oh yeah, I made my own biodiesel for 2.5 years.

euromodder 04-30-2011 07:00 AM

Welcome to ecomodder.

It's going to take more than a wee bit of hypermiling techniques and aeromodding to get to your goal.

There are some users on EM with higher MPG trucks, like users BamZipPow, Jiggerman or Big Dave.
Seek them out in the EM garage or in the forums, see what they've done, and copy whatever you can.

Weather Spotter 04-30-2011 11:56 AM

Welcome to EM.

I would recommend looking through our wiki for mod ideas and to see what each mod can do for you.

Car MPG Efficiency Modifications Main - EcoModder

RobertSmalls 04-30-2011 04:31 PM


Originally Posted by JustLuckey (Post 235123)
I'm open for other areas/ideas of improvement....with my list, I think the main issue is aerodynamics....which will be tough to keep a relatively stock look intact.

I agree on both points. However, perhaps you could start with a grille block made of black coroplast attached to the inside of the grille, in addition to gasketing the panel gaps with weatherstripping. Rear wheel skirts and a streamlined hard shell bed cap would be ideal, but those are harder to hide.

I would try to find ways to make aeromods look good, even if they aren't stock. e.g. a mudflap delete, or a large front airdam that looks factory, even though it was never offered on a Ram.

And welcome to EcoModder! The more engineers, the merrier.

blade 05-03-2011 10:24 PM

welcome to em. good luck

Diesel_Dave 06-03-2011 01:05 PM

Not sure if you're still out there JustLuckey, but I'll chime in.

I'm in a similar boat: I have a 2007 3/4-ton. I have the 6.7-liter rather than the 5.9-liter, but there's not a whole lot of difference. Mine is only 2wd and have a manual tranny (a big help). Your goals are reasonable: I've gotten 25.3 mpg on my last 3 tanks, and I've done 912 miles on a tank (I assume you have a 34 gal tank). I haven't done any aeromods yet, either.

I don't know if there's a difference between the 2005 & 2007, but removing the wipers is really easy on my truck. I can literally take them on/off in under 5 seconds. There's a little clip where they attach. You just flip back the clip and pull it right off. I take mike off and keep them in the truck. If it looks like rain, I pull out the driver's wiper and slap it on. I'm not sure how much it really helps, but I figure it can't hurt.

FYI, my OBC reads high as well (~2-4 mpg high). I use it to tell how well I'm doing, but don't trust the actual number.

You say you have a tuner, but a just running stock. Why? You can get quite a bit of mpg benefit by just running some good tunes. Also, you should be able to get a nice benefit from removing the EGR system, or at least turning it off with a tune.

I'm interested in you're electric fan install as well, let me know how it goes.

JustLuckey 06-03-2011 01:32 PM

It's been awhile since I've posted...I had my first child (my son, William) 3 weeks ago and have been focusing on him most of the time.

Anyhow, since I last posted, I got my flex-a-lite electric fan installed to replace the mechanical one. It's definitely much quieter, but it's too early to know if it affected fuel mileage. I also purchased a used (cab high) ARE bed cap last weekend. I'm hoping the combination shows another 1mpg or 2. I'll have a better idea when we take a family trip to GA at the end of the month. Although we'll be stopping more to feed my little guy.

I'm not real keen on removing the wipers. One of my main goals is not to remove the functionality and normal amenities of the vehicle. I'd hate to remove the wipers (even on a nice day) and forget and try to use them to wash off the pollen (in full force here in PA) and scratch the glass. Good thought though.

Regarding the tuners (I actually have 2). The first one I got was the Quadzilla MPG-MAX, that I upgraded to a Xilalraider (SP?). This one has a bunch of different factory tunes to choose from. It mainly does 2 things. 1) adjusts fuel delivery (if you floor it, it won't gush the fuel, it will slowly buildup fuel flow- bad for burn outs, good for MPGs). 2) Boost Fool, it will turn off the boost limiter, allowing the truck to go over the stock (24psi, I think on mine) allowing better accell. The QuadZ plugs in under the hood to the fuel mgmt system.
My other tuner is a BullyDog GT (Gauge/Tuner). It allows 'on the fly' adjustments (Stock, Tow, Performance, Extreme). I noticed that anything higher than Stock, produces a good bit of black smoke (read, unburned fuel). So that's why I normally drive on the stock setting. When I want more power, I will use the Tow or Performance. I haven't used Extreme, as it warns about possible tranny problems/breakage if you're still running stock tranny and/or stock torque converter (which I am running stock of both).

I will update in a few weeks when I do my 850+ mile trip to GA.

And yes, I have the 34 gallon tank that comes with the short beds vs. the 35 gal in the long beds.

bestclimb 06-03-2011 02:06 PM

regarding the wipers. I don't think they are talking about the rubber blades, but the whole arm.

euromodder 06-03-2011 02:30 PM


Originally Posted by JustLuckey (Post 242804)
It's been awhile since I've posted...I had my first child (my son, William) 3 weeks ago and have been focusing on him most of the time.

Congratulations :thumbup:

JustLuckey 06-04-2011 09:55 AM


Originally Posted by bestclimb (Post 242815)
regarding the wipers. I don't think they are talking about the rubber blades, but the whole arm.

OK, I misunderstood.

I don't want to split hairs, but for me, it's still outside my scope of mods. I can appreciate and I commend those who come up with unique ways of making their vehicles more efficient/aerodynamic, but my goal is to keep it as close to stock looking, as possible, without losing basic functions. If I make a mod, I want virtually no upkeep/work involved after the install. Like my LRR tires. Once installed, no extra maintenance.

In my situation, my wife drives the truck a good bit. (she also fills it up occasionally, which is why I don't always have a good gauge of my mpgs) Although she appreciates my efficiency interests, she doesn't want it to add steps or negatively affect her driving experience. I used to make & run biodiesel in my truck, but (in the winter) she would have to remember to hit a switch on the dash to turn on the in-line fuel and tank heaters. I love my wife, but she didn't always love remembering to hit the switch. I'll say no more....

I am going to continue to lurk and be interested in the knowledge, opinions, and posts on here.

Thanks for such an informational forum. I'll post eco numbers soon. Time to go feed my son. :)

Diesel_Dave 06-06-2011 01:50 PM

Congrats on the birth!

Regarding the tunes, just start trying different things and keep a record of your mpg on a regular trip (to work and back for example). Just see what works best.

My 6.7 engine has the advantage of a VG turbo rather than the wastegate turbo on the 5.9 so that probably helps the smoke. Also, the 6.7 has an intake throttle that needs disabled/removed to avoid smoke issues with a lot of tuners. I don't think that the 5.9 has a throttle, but you might want to check.

Diesel_Dave 06-06-2011 01:53 PM

Also, I don't think that you really have to worry much about a hot tune doing damage to your tranny, etc. --- as long as your just doing daily driving without much load. The only time I'd be concerned about that would be if you're really pushing the engine (towing a lot, etc.)

skyking 06-06-2011 02:37 PM

I sympathize regarding the wife. I purchased an auto so she would feel comfortable driving it some, but I keep adding doodads that are beyond "put it in drive and go". Totally to her credit she has driven the truck/5th wheel combo with relative comfort.
I have a powerful exhaust brake that also has the annoying function of locked shifts from 3rd to 4th. I remember to either let off the throttle or have it disarmed, but I can't expect her to do all that.

backyard engineer 06-06-2011 11:19 PM

congrats on your little boy. I'm glad to hear of your willingness and interest to conserve. any and all efforts are appreciated if only from afar.

slowmover 06-07-2011 06:26 AM

Nice numbers thus far!

I'd be careful about having replaced the mechanical fan if heavily loaded or contemplating towing. DODGE would have gone to them (as would makers of big trucks) for FE reasons long ago if they were capable of moving as much air as a clutched mechanical fan. They aren't. I leave mine as is for the practicality of the wide range of work a truck can perform. A truck is either income-offsetting or income-producing. If neither, then another vehicle is warranted. Frankly, the fan change is a crippling move.

In that same vein there are problems that bear investigation, especially on the 4WD models, namely, steering and front suspension component that wear somewhat fast and are re-engineered on later models. Plenty of threads on upgrading on Dodge-specific forums. (Same for HVAC performance, etc). All of these are "economy" in that we are increasing the per-mile cost of ownership, however reluctantly.

The first step for truck FE, IMO, is very careful record-keeping. Understanding the costs as expressed in a cents-per-mile format. An understanding of truck use (percentage highway vs percentage city) is only seen through records, not "what I think it is". Average mph and average mpg go hand-in-hand together. One begins by forecasting ownership life and annual miles.

For truck FE: Truck spec is first, terrain/climate is second, and driver skill is third. The first two cannot be changed, only accommodated. The third is ripe for exploitation if one can get some distance from the usual emotions around driving, primarily the convenience of 24/7/365 usage. Restrictions of use -- such as no single trips (combined trips only) -- are a good first step to see what works. And roll into that a "No Left Turn" policy such as UPS uses.

The difference between the best and worst professional drivers is 30%. Call it a one-third difference in the amount of fuel used to accomplish the same task. Same truck, same work.

Thus I have little patience or belief in aftermarket gizmos that only add to cost -- some with the propensity to shorten vehicle component life -- and the use of which tends to overshadow driver skill improvement (and the gizmo is given credit). A stock truck is the best baseline, and for a factory-delivered Dodge maybe a camshaft change plus timing advance is worth 1-2 mpg annually assuming LRR Michelin tires. (Modified trucks are so far out of spec as to be worthless for comparisons unless one can find an exact match as to spec, terrain and use).

The aftermarket gizmos also increase depreciation and add to the "initial purchase price + finance cost" line of a spreadsheet. One can go through the items mentioned each by each, but let's admit that wishful thinking is part of the "equation" (unless, again, we can corroborate the changes with a similar spec truck in a similar climate/terrain and cross-our-fingers hope that driver skill is similar and that records are honest).

For what it's worth I'd can the go-fast stuff and look to other changes as mentioned; tire spec being the single-most critical change after safety is covered. Bed cover, grille block, air dam, belly pan, etc, can all be experimented with cheaply (and some great stuff to read around here per some other owners).

Start with wheel-by-wheel weights from a certified scale when "empty" (full fuel plus driver plus normal stuff in truck), and scale again (axle-by-axle) when loaded. A stack of scale tickets is handy for comparison purposes. I did this initially to set trailer hitch rigging, but found that it was also useful in predicting FE for a given trip. IMO, if one cannot predict the mpg of a given trip, then more homework is needed. Same thinking for tire & brake life: less than 70k on either (for an on-road vehicle) then the driver is in need of remedial training.

Proper tires, proper alignment, and detailed attention to mechanical drag (system by system) is the first "real" step after complete records establishment. Maybe manual hubs will help, for example. I've seen reports of yes & no. Aero improvements are only relevant to a truck that spends enough time above 50 mph to actually recoup costs. An in-town commuter, a local contractor, is unlikely to see enough change to matter.

FE will be the percentage change of average (overall) mpg change from baseline. If my annual mpg changes from 22.48 to 23.61 mpg over 15k miles, then I am on the right track. 5% has meaning, here, where "1-2 mpg" does not. The particular "blend" of steady state highway speed versus in-town stop-n-go is nullified when looking at changes in this manner.


Diesel_Dave 06-07-2011 11:13 AM

slowmover, just a few comments on what you said.

1) On the fan, you're probably correct. My thinking is a CLUTCHED mechanical fan is probably superior to an electrical fan from an efficiency perspective because there aren't the conversion losses ( I can see where an electric fan would have an advantage over a non-clutched mechanical fan). Also, unless you're doing a lot of driving where you're really working the engine at low vehicle speed, I don't think you're clutched fan is going to run that much anyway.

2) Your note on careful record keeping is right on. If you're not doing that you're just fooling around.

3) I totally agree with your point that you have to think about all mods from a TOTAL cost perspective, rather than only a FE perspective. If you spend $1,000 on something that improves your FE by 0.1% on a pickup you're crazy.

4) Regarding the "aftermarket gizmos", I have to disagree somewhat with what you said. You really have to look at things on a "gizmo by gizmo" basis. You are correct that some mods are going to result in premature failure, so don't do those. However, some mods will actually increase your mechanical life IF done correctly (removing EGR for example). The key is to be patient and really understand what you're doing BEFORE you do it. Know what to do. Know how to do it. Know why to do it. You should research the whazoo out of a mod before you go out and do it.

5) Maybe I misunderstood you, but you seem to have the idea that, "If it led to better FE and/or better engine life, then the manufacturer would have done it so don't mess with anything." This I have to disagree with. The one thing that you're forgetting about is emissions regs. Engine manufactures have been forced to add components and calibrations that significantly hurt initial cost, engine wear, and fuel economy. Case in point are the DPF's (diesel particulate filter). They add a bunch of initial cost, a bunch of maitenence cost, burn a bunch of fuel (both in regens and added backpressure), and they prevent the driver from driving effectively for FE because you need to keep your exhaust temps up.

All that being said, I geneally like the way you think!

slowmover 06-09-2011 10:32 PM

Bear with me, this isn't as adamant as it may sound.

As to case-by-case basis the two I mentioned seem to be the ONLY ones, that, together produce changes in overall average annual fuel economy (working from a solid baseline and stock truck). The magic boxes only "may" produce an increase, typically in only one mode of driving: stop n'go. The timing advances make it easier to not hang shifts (manual) and make life a bit easier for autos. The "evidence" for steady-state fuel economy increases -- highway -- pretty well doesn't exist. (This understanding is taken from the main guy at the best known aftermarket Dodge tuner; all my wording, however.)

You may be the person to allay the concerns: solid mechanical baselined truck, highly extensive records, and the education to pull off a set of proper tests (given the exigencies of private life and budgets) once the parameters are clear to you. Hope you'll give us Dodge guys another piece of ammo to chronograph!.


Diesel_Dave 06-10-2011 01:31 PM


Timing advances (almost always) increases engine thermodynamic efficiency--both transient & steady-state. There's not really any mystery about that. You can get the information from any basic engine textbook.

There are 2 warnings, however, about advancing timing.
1) If you take it to an extreme, it is possible to advance the timing too far. When this happens your FE will come back down. You'll also start getting black smoke. Back in the day (before we had to worry about NOx emissons) a rule of thumb for setting the timing was to advance it as much as you could until you started getting black smoke.
2) Be very careful about advancing the tuming significantly if you're going to be running at high loads (heavy towing, etc.). Advanced timing increases peak cylinder pressures. This helps your FE, but if you go too far you can cause mechanical damage. If you're not pushing the engine you don't have to worry about it because the cylinder pressures aren't anywhere near the limit.

FYI, I've done diesel tuning for years and if you want to increase FE the easiest thing to do (tuning-wise) is to advance the timing. Engine manufactures can't advance the timing that much anymore because the NOx emissions also go up.

Here's a simple graph from an old research paper:

slowmover 06-11-2011 09:35 PM

Thanks, DD. I should have posted that there are DIY mods ("tone ring" on CTD) that are pretty well free, versus a $600 gizmo. I'm well aware of changing timing to more optimum specs (and you did a far better job than I would have in explanation).

The unanswered question -- as always with engine programming -- is what else is affected? Even subtle changes can have long term impacts that the short-term owner (5-7 years) has no "reason" to care about (as his purchasing decision is emotional, with only a nod to potential consequences) as the truck is long gone once issues of wear & tear begin to surface.

Diagnosis of problems is kept within bounds as aftermarket gizmos add complexity to decision trees. Of course, there is no in-depth explanation by the aftermarket as to what parameters are changed, and we are in the dark with -- at best -- SWAG to work with. The "improvement" may wind up costing more (much more) than the purported savings; thus my cautionary stance. (We are to put ourselves, IMO, in these shoes: my job has disappeared, my wife is now chronically ill and the need for the truck has become paramount . . . . )

Having owned many "old" vehicles [daily drivers], and driven 3/4-million mile trucks one is always stymied by a previous owners attempts at "improvements" . . from which I do not except myself. The dead stock vehicle tends to have the longest life for the lowest cost. A very high tendency. A 50k mile reduction in useful vehicle life is no small consideration (as an example). A truck has no substitute for itself as does a car as it is much more than private transportation. It is central to the income of the owner (whether an individual or a group). The loss of an otherwise good truck is little different from having to search for a new employer when understood properly.

EFI Live is a new (to CTD) program that allows the user to tailor engine operation profiles. Could be one will do more or less hypothetical damage, but at least the inputs would be clear during experimentation. At least I know whose tail to kick if things go wrong.

Looking forward to this thread progression. There is a dearth of genuine interest in fuel economy in diesel pickup trucks.

Diesel_Dave 06-13-2011 11:00 AM


I think we actually agree on more than we disagree on. Mainly, people shouldn't play around with changing things that you don't understand. I guess I just come at things from a slightly different perspective because I've worked in diesel R&D for several years.

Backtobasics 06-13-2011 03:00 PM

One thing I have not read in this thread was propane injection. While I am not thoroughly versed, what I have read is that it is great at cleaning up an overfuel truck, but that it also can be programmed, to augment the diesel used, extending range, and increasing MPG.

quick searched article here, on Dodge:
Dodge Ram Cummins Diesel Propane Injection Performance | Mopar Muscle Magazine Article at

slowmover 06-13-2011 05:16 PM

Propane injection works well when the cost of propane is low, relatively. The btu content per "gallon" (rough equivalent) is lower than diesel; maybe 2/3'rds. In some states (Utah) this is $$-efficient. In most others one simply has a dual-fuel vehicle to extend the range of available diesel (were there a shortage). The cost is easier to absorb than a CNG (compressed natural gas) conversion/addition, but CNG stations are fairly rare (search for nationwide locator); one can also spend $$$ for a home compressor station. Propane is widely available nationwide (and be aware that one must pay road tax for fuel in either case; an expensive citation if not properly registered).

Both add complexity and weight to the truck, not to mention reduced space.

Both should also be viewed on a graph comparing also WVO and WMO.

The great thing about a diesel is that all can be considered.


slowmover 06-13-2011 05:24 PM


Originally Posted by Diesel_Dave (Post 244850)

I think we actually agree on more than we disagree on. Mainly, people shouldn't play around with changing things that you don't understand. I guess I just come at things from a slightly different perspective because I've worked in diesel R&D for several years.

I also believe we do. Very few of us have, however, the knowledge, skill and tools to gauge the condition of an electronically-controlled diesel engine. A gasser is simple in comparison (and everything is far cheaper) when it comes to assessment.

On the other hand I'd take chances with a $6k gasser longblock (engine cost) that I never would with a $18k Cummins. Had I a cousin at the local CUMMINS dealership I might be more willing. If I knew of fleet comparisons I'd be more willing to try aftermarket parts. The usual enthusiast crowd is short-term ownership and abusive, by definition. (And I won't leave out those who use trucks for their livelihood as I've seen too many with no feeling for, or records of, proper maintenance procedure. For just a start).

What we do has to work. If we have no way of gauging long-term effects then the gizmo is suspect from the beginning.


Dad 06-15-2011 08:29 PM


Congrats on the birth of your son!

I also have a 2005 Dodge Ram 2500 4X4 CTD but mine is a LWB and has the G56 6-speed manual transmission. I LOVE my truck. My best (hand calc) FE in the truck is 22.5mpg, but I'm usually in the 21-22mpg range most of the time. Everything is stock on the engine, stock wheels and tires, and stock ride height. I have a Pace-Edwards JackRabbt tonneau cover that helps a bit with mpg's. Also, I tried the tailgate removal trick, and my mpg's actually went down slightly. My best mpgs are with the tailgate up and tonneau cover closed.

IMO, these trucks can probably be pushed to higher mpg's, but what I ran into is that these Cummins diesels don't like to loaf along under light load for too long or they complain. They're meant to be worked, and if you don't work them, they get sluggish, run rough, and suffer from wet stacking (washdown) leading to increased fuel dilution in the oil. Just not worth it, IMO. I ended up having to run the truck hard periodically or hook it to a load just to prevent too much cylinder washdown and get it running right. And that negates the FE efforts. Also the Cummins is just not conducive to many hypermiling techniques such as FAS-ing. I love my truck a lot and refuse to part with it though. I have 170,000 miles on it and hope to run it at least another 170,000 miles. But, I finally decided it was more efficient for me to park my truck and commute to work in my minivan instead. The fuel cost savings alone on my 140-mile daily commute, along with carpooling, actually is enough to fully cover my minivan's loan payment and then some.

I'll be interested to see your progress in eeking more mpg's out of your CTD though. One thing to consider looking into is getting a programmer that will eliminate that third injection event, which only serves to clean up the CTD's emissions. My understanding is that you can pick up another 1-2mpg just by making this mod. Maybe one of your existing programmers already has this capability. Good luck!

slowmover 06-16-2011 12:00 PM

what I ran into is that these Cummins diesels don't like to loaf along under light load for too long or they complain. They're meant to be worked, and if you don't work them, they get sluggish, run rough, and suffer from wet stacking (washdown) leading to increased fuel dilution in the oil.

I read this in other places online, but find no verfication. Oil analysis or Dodge TSB re-flash, or?

If one runs the truck lightly then the ECM adjusts to that. If one is loaded heavily, then the ECM adjusts to that. Remaining in any condition just long enough and the computer will use accumulated data on the most recent several hundred or several thousand miles. I can park the trailer and notice that the truck is "peppy" compared to use when solo until it re-adjusts itself. That is not performance degradation. If it were, we'd see CTD life as short as too many Fords or GM diesels (ha!); really, a motor running that way has a shortened life.

Our two trucks are not identical stock from factory, granted. Yet it's fair to state that what you've described as a One Note Johnny engine (only works well under a prescribed condition) is not borne out by much other experience, and, without verfication, is suspect. I might remember to go WOT once a month or so, and I might remember to use some fuel treatment once a year (usually now, during hurricane season). Were the premise stated correct then I would see a degradation in FE due to my use. I don't. This time of year I break my self-imposed "no idling" rule as it is too danged hot. This single factor reduces my in-town economy as shown by a decrease in average mph. Light loads and light throttle are just fine with an HPCR CTD.

Hope to read more of your experience with that truck (and all other CTD's). The bed cover and tailgate "up" is backed by much experience, and by expertise (from the OEM manufacturers, among others). Reduction of rolling resistance is the place to spend money, IMO, and the experimentation (mainly on this site) of aero aids to pressure drag reduction will pay some dividend if highway miles are high enough to justify them. The cheap DIY approach, here, is great (versus the cost of aftermarket toys so many are enamored of for pickemups) for investigation of pressure drag reduction.


Diesel_Dave 06-16-2011 01:46 PM


I really wouldn't be concerned too much about fuel dillution at light loads unless you have some info from an oil analysis showing it. Since the advent of the common rail, the injection timing is adjusted for different speeds & loads. Older, mechanical fuel systems had to keep the same timing everywhere. Especially if you're running stock, I would be suprised if you had any issues. That being said, if you're concerned about it just have an oil analysis done.


ECM's don't "adapt" over time. In some cases, it can go into or out of different control modes/look-up tables (steady-state, transient, high altitude, etc.), but the ECM doesn't "learn" anything. Eventually, that might happen (I've talked about it a little with other folks in the industry) but it's not in production today. The technology is actually out there to be able to do such things. One of the biggest problems, however, is dealing with the EPA--how can you prove to them that it will always meet emissions if it's always adapting itself? It's not impossible, but it's really difficult.

I'd say the difference that you notice after pulling your trailer is psychological. Just like like when you ride in a car again after driving your truck so much and it feels so wierd that you're sitting so low to the ground.

skyking 06-16-2011 01:56 PM

Thanks again Dave. I dream of an affordable adjustable timing gear for my old 12V. As it sits, I must go with what works best.
12V + mappable timing = pure win, IMO.

Dad 06-16-2011 03:38 PM

Thanks for the added info guys. Yes, common rail injection has provided dramatic improvements in diesel efficiency. Only downside is that these common rail systems are a little more sensitive/finnicky, but careful attention to fuel quality and filtration takes care of most of that. Although I still have concerns about this ULSD and its possible negative effects (shortening their life) on these injectors.

Anyway, my concern is based on two things: 1) Oil analysis from Blackstone Labs. I had a test done on an oil interval that was all unloaded commuting and compared against oil analysis from running loaded and dilution was up substantially on the unloaded interval (something like 3% running unloaded vs less than 1% loaded). It was a few years ago so I'll need to see if I can dig up the reports to give you exact numbers. 2) Personal observation. After running light unloaded for some time, the truck's performance becomes quite sluggish. Then when I hook up some weight behind it and run it hard for a while, then unhook, it has all its power and economy back again. It seems to respond well to the old "Italian tuneup," in a sense, to clear it out and clear the unburnt fuel. Also, after loafing along for a while and then getting on it, it blows quite a bit of smoke for the first couple WOT runs until that unburnt fuel is burned out of there. You guys with the newer 6.7's may not notice this much, but the old 5.9's do it. Anyway, while the common rail injection system is dramatically improved vs the older mechanical injection, I do still tend to believe they don't quite run optimally at very light loads. It's probably not quite achieving complete combustion of all the fuel at very light load, but that's just my guess from what I've personally observed. Anyway, maybe there's more to the story that I don't know, but based on what I've learned and research so far, this is what appears to me to be going on with these CTD's. Despite this, I still love my truck and they'll have to peel my cold dead hands from the steering wheel to get me to part with it. :)

slowmover 06-19-2011 12:33 AM

Despite this, I still love my truck and they'll have to peel my cold dead hands from the steering wheel to get me to part with it.

Yup. Best vehicle I've ever owned on a cost-per-mile against potential work-per-mile basis. A Camry for mpg, but can pull a house down the road. DD, I'll grant you the word on the ECM, for now. As to dilution I'd like to see numbers as I believe only extensive idling (as a percentage of total hours) will show a rise on an HPCR (given a truck with no magic gizmos attached).


wilcorp70 06-20-2011 08:41 PM

Seriously, more people need to think about aeromodding their big trucks. My uncle drove an 18 wheeler, and I swore I could have cut his fuel bill in half with a lot of fiberglass and bondo.

DieselFan 08-30-2011 05:24 PM

Hard to believe those numbers JustLucky but I certainly like your detailed explanation for such results so I am going to believe it's possible and see what I can learn from it!
I have a 2003 RAM 3500 Long Bed 4x4 with manual 6sp and I do get the exact same figures you used to. I have no mods except for a Quadzilla Mileage Max that I have run for over a year now. I have always hand calculated my mileage since new and can certify that over a full two-year test, one with and one without Quadzilla, the difference has been absolutely zero on mpg. I have now on order a Smarty Jr that will enable me to dial in some fuel timing advance. Hopefully that will improve measurable my mileage. I am runing OEM size tires, 265/70/17 Pirelli Scorpio ATR and they will be replaced next summer with Michelin LT MS 2 like your but they need to be E load rated. You said you installed skinnier tires, what are the dimensions and what load rating are they?
Would you be able to give an estimated break down of how much mpg you gained from each of the mods. I would like to ne able to make an educated decision as to what I need to do next to my truck to reach my ultimate goal of 25 mpg on the highway at 65 mph. Not as aggressive as yours but my truck is a big 3500, has a fiberglass high top canopy, running boards, mud flaps, deleted front spoiler (off-road incident) the big towing mirrors, etc.
Any detailed info very welcome.
Diesel Fan

oil pan 4 08-30-2011 07:34 PM

Back in 2007 I went to a 2 inch taller, an 1 inch wider and over all much heavier tire and saw no change in fuel milage on the highway or city. If anything it went up.
I went from a P-metric to a load range C floatation size on a 15 inch rim.
Going to a taller tire dropped my rpms needed to maintain 65mph by about 50rpms.
Lower cruse RPMs with high inflation pressure is what saved me.
Now all I will put on the truck is 31x10.5R15 size tires.

On a 1 inch narrower tire in load range C it can mean the difference between 2300 pounds per tire and 2000lb tire. Thats a 1200lb difference.
With just me in my truck it weighs just under 6000lb with an near even 3000lb per axel. With a 9.5 inch tire I would be driving around 75% loaded, even with the truck empty.
Not good, I don't like to load them over 90% (in summer heat).
If I add 1000lb over an axel that maxes out the tires. Its not hard to do when towing a trailer.

10.5 inch tires on the other hand give a better margin of safty. They are only about 65% loaded when empty. That gives me 4600lb per axel to work with (1600lb per axel after you add the rest of the truck).
Now if I put an extra 1000lb over an axel I am running about 87% load. I like that.

I never thought about it till I over loaded the tires on my truck and had 2 blow outs pretty far from home. Not fun.

slowmover 08-31-2011 04:14 PM

I would like to ne able to make an educated decision as to what I need to do next to my truck to reach my ultimate goal of 25 mpg on the highway at 65 mph.

Hope you'll search around on other threads for more info. But a 4WD is hard put to reach above 20-mpg very far due to the real increase in rolling resistance (drivetrain) and aero pressure increases (vehicle height).

You might consider the Tone Ring Mod as a cheaper alternative to the Smarty Jr.

The MICHELIN LTX A/S is a better LRR tire than the LTX M/S. (There's a retired engineer in Alberta running oilfield hotshot in a 2WD; he runs NOKIAN HAKKEPELITA in the winter, and an LRR in summer; over 20 mpg on his 2006).

See all threads & posts by DIESEL DAVE and BIG DAVE as a starter.


DieselFan 09-08-2011 10:31 AM

Hello Just Lucky,
Please can you be more specific about which Michelin tires you are running and the dimensions? Are they E load rated?
I need to replace my Pirelli Scorpion ATR, currently 265/70/17 in E load rating and have been considering Michelins but there are many options. I want Low rolling resistance but need to retain the high load capability.

slowmover 09-08-2011 01:12 PM

DieselFan, the MICHELIN LTX A/S in oem 265/70-17 is a 121-factor Load Range E, LRR tire. The stock wheels can carry no more, and the RAWR is less than the combined tire weight capacity. The M/S may be LRR rated, but the highway rib A/S is superior from the standpoint of FE (where the M/S is likely better on wet pavement and non-solid surfaces).

I got 120k miles with 4/32's remaining on the original set, and will come close to 250k miles when the first replacement set is ready to be replaced. Expensive up front, but cheap considering the lifespan. My experience is not unique, nor are all miles on highway.


DieselFan 09-08-2011 01:55 PM

Hi Slowmover,
Sounds like you're reading the site today so I'll chance another question!
This one related to our thermostats.
I am running the Dodge dealer thermostat and my temperature is very stable but always below half mark on the dash guage so I just installed a Scanguage II and sure enough, reading is consistent at 182-184 F.
I have read many say that we would gain mileage by running closer to 200 F and many posts seem to indicate that our OEM thermostats are 190 F so I changed the thermostat thinking it was operating lower than spec and installed a new dealer thermostat, I don't want a NAPA, bad reviews. Results are still giving me a low 182-184!
What are others runing the 5.9 L Cummins seeing?
Is there a Cummins part # for a 190 or even 195 F thermostat for our engines?

Diesel_Dave 09-08-2011 05:25 PM


Originally Posted by DieselFan (Post 260114)
Hi Slowmover,
Sounds like you're reading the site today so I'll chance another question!
This one related to our thermostats.
I am running the Dodge dealer thermostat and my temperature is very stable but always below half mark on the dash guage so I just installed a Scanguage II and sure enough, reading is consistent at 182-184 F.
I have read many say that we would gain mileage by running closer to 200 F and many posts seem to indicate that our OEM thermostats are 190 F so I changed the thermostat thinking it was operating lower than spec and installed a new dealer thermostat, I don't want a NAPA, bad reviews. Results are still giving me a low 182-184!
What are others runing the 5.9 L Cummins seeing?
Is there a Cummins part # for a 190 or even 195 F thermostat for our engines?

You're probably running a 180 F thermostat. That starts to open at 180 F. My truck has the 190 F thermostat and usually runs ~200 F (+/- 5 F) when warmed up. Here are the Cummins P/N's:

180 F: 4990285
190 F: 4929644
200 F: 4929642

EDIT: P/N for 180 & 200 should be reversed (200 deg is 4990285)

slowmover 09-08-2011 05:42 PM

The Cummins-brand thermostat is the one to have by what I have read. It opens partially at around 190F on mine, and comes fully open at 207F (which I have recently confirmed on mine; see miles in sig). Your year and model may be different slightly.

One must remember that a diesel is a highly stressed engine (cylinder pressure) and that, once the truck is doing the work for which it is designed, that the oversize cooling system becomes "adequate". Those who add gizmos, tuners, etc always run the risk that the extra fuel and engine timing will exceed this capacity (first noted on EGT; exhaust gas temperatures which exceed design parameters). Indeed, for towing, one is better off without them. There is no free lunch in the production of power without a trade-off. And, as cooling systems are the vehicle system most likely to be neglected (by all owners of all vehicles), it takes it in the neck.

This long preamble is my way of saying that I am aware that others have searched for alternate temp stats and found only -- to my knowledge -- slightly lower temp ones. I would say that, to raise coolant temp as measured currently would have only a minor benefit, but both using the oem block heater daily, and installing a grille block (partial; upper is what I'll try) one may be able to raise coolant temp faster, thus raising oil temps faster; or, on a marginally cool day with a long drive, raise combustion efficiency/lower internal friction to make the "risk" worthwhile.

We all of us -- race boys and hyper-milers -- tend to forget that the truck as a solo vehicle is almost outside of it's operating envelope. We always take a risk with component, system and vehicle reliability & longevity when we look to alter parameters to "improve" but one of many for which the truck is designed.

I do not ever wish to compromise the ability of the truck to do work. If that means slightly lower mpg -- the stock configuration -- so be it. There is plenty I can do to lower my overall cost of ownership of a particular vehicle and still have it do the same work as before. The expense of keeping one of these in like new condition takes more money than most will spend. They'll just "wear it out" in the expectation that there is always a new one around the corner . . never considering that what they drive now may be the very last vehicle they ever own.

Seen from this light, one has to plan -- to budget -- to replace things before they wear out. Failure affects other systems, not just the other components of the same system. Correctly done, one replaces entire systems before they fail, not a component here and there. To sum up: the cooling system works in a prescribed manner with some delicate components dependent on particular temperatures and chemistries. To alter the balance in order to force one outcome over others is to put reliability into question and to shorten longevity. These are highly expensive engines, so need I say what I think of those who like to hot rod these trucks?

You'll notice that those who get 1-million miles from a CTD are those who leave well enough alone and follow (or shorten) factory service intervals; in a good relationship with vehicle service facilities. Were I you, and asking this question, that is where I would spend this energy: a complete set of factory Field Service Manuals, and time taken to determine the best techs and mechanics in my area.

It's your truck and you'll do as you will, but, having asked my opinion and seen how I've learned (partly the hard way; that's where the above comes from) that some guiding principles must be in place, first, before ever operating one of these. Principle One: Leave well enough alone. Most of us are okay with maintenance schedules and the costs therein. But, emotionally, our society encourages immaturity in the costs of repairs. Just get a new one . . . .

Gasser engines are easier. And dirt cheap by comparison, practically disposable. "Mistakes" are easier to live with, too. A medium duty diesel deserves much more respect.

This has been my long way of saying that there are no easy magic gizmos or parts substitutions that will, in all ways, lower my cost of ownership. The opposite is not only more likely, it is more likely true. Be careful with your choices: the day you need to work it hard, will you want to change the thermostat?


DieselFan 09-08-2011 10:36 PM

Thanks to both Diesel Dave and Slowmover.
Both of you have thermostats that open around 190 F from your answers.
Mine opens at 181...
I also fully agree with your detailed opinion slowmover, these engines should not be tampered with unless you know what you are doing and they are very well designed to start with.
My reason to want to change thermostat is simply to obtain same temps as others are!
Strange enough, I went to a parts store selling only truck parts and for my engine he told me that Cummins only lists the 180 F thermostat.
Mine is the HO 305 hp ISB 5.9 L in 2003 vintage.
How come yours have a different thermostat? Do you have a different engine? Is is the standard output or a different year?

Diesel Dave, the three part# you gave me would be for which engine precisely?

Many thanks guys.

JustLuckey 10-26-2011 12:32 AM

Sorry guys for being absent for quite some time on the thread I started...between working and being a new dad....doesn't leave much room for forum following and posting. In my absence, there's been a lot of good info, recommendations, and discussion in this thread. Thanks, good reading to catch up on. Also, hello to my fellow cumminsforum and dieseltruckresource friends!

I spent quite some time looking through the aero bed cap threads...I felt like I had a bit of attention deficit disorder when trying to follow that thread that branched off to a 2nd thread, then a 3rd...then finally circled back to this one I started earlier this year.

Before I get too far into my post, I want to apologize for a inaccuracy in my initial post (as a reread it and all that followed). I originally posted that I get 24-26mpg on the highway. This is not correct as I have found out later. Let me explain....
I make several trips from PA to GA each year. In prep for the trip, I literally fill my tank at a station, return home, then use a 5 gallon container to 'top-off' my 34 gallon tank in my driveway (so I have a true FULL tank before leaving the next morning). This top off includes waiting for the air to bleed (on a quiet day, you can hear the whistle of it escaping) and rocking the truck. It will often take 2-4 more gallons after the fuel pump clicks off. Then I'll do my 800+ mile run and fuel up somewhere in SC. The SC fuel up is where my calcs are thrown I don't get a true 'fill-up'...often missing the 2-4 gallon top-off. Having said that...

My trip to GA in late June 2011 had 2 fairly new mods (electric fan and cab high ARE Cap, vs. my hard tonneau cover).
I took pics of my odometer at each 100 mile mark (seen here: www(dot)cumminsforum(dot)com/forum/3rd-gen-powertrain/360834-whos-traveled-farthest-one-tank-7.html (replace dot with . ) Who's traveled the farthest on one tank? - Page 7 - Dodge Cummins Diesel Forum) until I hit 800.5 miles, where I filled up. My wife had to feed my baby boy, so I was able to spend the 15-20 mins (with the help of a very low flow setting on the pump) to bleed out the air, rock the truck, etc to get a true FULL tank of 36.65 gallons (well over the 34 gallon tank that I have) for a mark of 21.84 mpg.
Then during my trip to GA in Sept 2011, I was by myself and it included another mod, a new aFe exhaust manifold...this is was an excellent time to check my mileage. I did take pictures of my odometer, but unfortunately, I didn't remember to email them to myself like I did last time (read: backup) and my phone died the next week and realized they weren't saved on my memory you'll have to take my word for it. I stayed in SC with friends this time and would be doing some city driving the next day, so I didn't hit the 800 mile mark, but would have crushed it otherwise. I filled up at 766.0 miles with 34.2 gallons for 22.4 mpg using my same 'top-off' technique. Also, my low fuel light (normally at 62 miles remaining / DTE) didn't come on until a couple miles before the fueling station....meaning I could have gone at least another 80-100 miles.

Sorry I don't have a good baseline for mpg, but I can say that I have never been able to travel those distances in the past...I remember my first trip to GA in my (stock) truck (when I first bought it in 2008), I barely made it 700 miles on a tank. Each trip I seem to be able to stretch it further and further. Any anyone that has traveled interstate 84 in PA and I-81 from PA thru VA knows that there's a lot of hills and mountains...and the upstate of SC isn't flat either. I will be the first to admit the obvious, my tests are far from 'controlled' tests, as temperature, speed, A/C use, and other factors a constantly different each time....but each time I do get further.

Let me see if I can address a few questions/issues that were aimed towards me.
I'm running on the Michelin LTX M/S2 LT235/80-17 load E tire, which is an all season / low rolling resistance (LRR) tire (versus LT265/70-17 General <Something> which was my stock tire). Not a huge difference in dimensions <1" taller and ~1.5" narrower. But these are rated at Low Rolling Resistance, so presumably more fuel efficient. The reason I didn't go with the A/T2 tire (which is also an all season tire) is that Michelin's website rates the M/S2 tire as longer wear life and more fuel efficient over the A/T2 tire.

I agree that keeping records of every fill-up and mileage is one of the best way to track mileage and effects of mods performed. But in my case, it would be very difficult. I spend most of my time on the road traveling to client sites in NYC and upstate NY (which I'll take my Camry). This leaves my wife with the truck (which she likes driving). She tends to have a heavier foot than I do, but also has our baby with remembering the receipt and/or jotting down the mileage is low on her list of things to remember at during fill-up. We also use a shopper discount card that gives us $ off per gallon, but the max is 20 gallons. So once or twice a month, we only get 20 gallons of fuel, not a full fill-up. These factors make is very difficult to keep good track of fuel in/mileage out. The only time I really have full control over mileage and fill-ups is during my PA-GA drive, when I drive the whole way and do the filling up.

I somewhat agree on 'gadgets' that claim to improve mileage. I have purchased a few (what can be considered) 'gadgets', but I do quite a bit of research before making a purchase and/or modify my vehicle. On an aside, a side benefit of traveling is 'points' accumulated on my AmEx, which can be converted into $ to be used on So most of my mods (my flex-a-lite fan, my exhaust manifold, and others) are 'purchased' for much less than retail. On the same line, I don't always purchase efficiency mods and labor based on a cost/benefit analysis. If I did, I probably would have just bought a smaller vehicle and call it a day. I'm after the hunt for the best mileage, not necessarily the hunt for best ROI. It may seem counterintuitive, but just like horsepower freaks don't factor ROI when upgrading for more ponies in their Mustangs, Hot Rods, etc...I'm the same way with MPGs. But I'm not willing to buy a $5k turbo or $10k tranny to gain 1% fuel economy (if one was proven to exist).

Regarding electric fan vs. mechanical/clutch fan: to each their own. In my research, it appears that the electric fan is more efficient and puts less stress on the engine. Yes, it needs electric, which comes from the alternator and/or batteries, but is the alternator demanding more from the engine when the fan is running vs the mech fan? But is that offset by having a lower runtime to cool down? I'm not looking for answers here or trying to spark more debate on this topic (if you do, please start a different thread). I decided to take the plunge and install it. (if you prefer the stock fan, then a differ on the issue, no harm done).

Regarding the question about why I have my (BullyDog GT) tuner but kept it on the stock (no added power/level 0) setting. The TOW (level 1) setting is a good all around setting that makes more power but I can't tell if it's better economy. But what I do know, is when I'm given more power (level 1, 2, 3), I have a tendency to use it more (read: WOOT!) which typically leads to worse fuel economy. Also, when I stack my programmers (with Quadzilla), when the Quad MPG-MAX is in it's default (MPG) setting, it can't be 'stacked'. So I have to leave the BullyDog on level 0. There are other Quadzilla tunes that do allow for stacking with the BullyDog, so I can use the higher level power settings.

Regarding propane (or natural gas) injection. I like this approach and the results. The results are proven in many studies that introducing a seconary fuel source that makes a more complete burn of the diesel fuel yields more power, better efficiency, and less (for most of the GHGs) emissions. This is also true for water/methanol injection. This is another topic I've done a lot of research on. In my case, I'm not too thrilled of putting a LP(or CNG) tank in my truck bed for safety reasons and taking up precise cargo room. The h20/meth injection is a little more reasonable (for me, at least), as the storage could be (at least, partially) in the existing washer reservoir (but i would probably need to add another 2-5 gals somewhere) plus the (20-50% mix of methanol) is a much less volatile solution than LP or CNG. And a 5 gallon square tank in the corner of the truck bed doesn't take up nearly as much space as some of the LP/CNG tank systems I've seen. Also, I used to make biodiesel and have a supplier for neat (clean) methanol. But (if you recall my early posts here), it would violate my rules for wanting to keep maintenance to a minimum (if h20/meth ran dry, a manual switch off is needed without 'rigging' something to be more automatic). Also, the initial cost is a big factor. $800-1000 for the system (Snow performance) that I want is a lot when there's still the methanol to buy and maintain.

In summary in my long-winded post, I'm still pondering over what to do next. Aerodynamics, Locking front hubs, h2o/meth injection, fuel/air seperator, etc....I need to put much more thought and research into these. One easy one that I haven't done yet is find and put the plastic wind deflector that installs under the front bumper on. The previous owner (for plowing, I beleive) removed it and discarded it. That may help a bit with aero.

I guess that's it for tonight. It took me almost 2 hours to write this up as I wanted to make sure all my numbers were right. Good night!

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