Hello, I drive a big truck and I like efficiency

[DieselFan]

Hmmm,
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]

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]

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]

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.
Thanks

[slowmover]

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]

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?
Thanks

[Diesel_Dave]

Originally Posted by DieselFan

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?
Thanks

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]

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]

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]

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 off...as 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 card...so 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 her...so 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 Amazon.com. 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!