All these replies right on the money, including Shorts. +++1

The Yukon is no comparison. Look at the size of the fifth wheel trailers being towed with these trucks. Way beyond the Yukon's ability. Compare a one ton gas powered pickup to a one ton diesel. Big fuel savings, and the diesel has so much grunt. That is what you bought. If you don't need it trade down. It takes energy to move the weight and push the air aside.

1450 - 1500 rpm is about as low a rpm that you will get any boost on the turbo. 1750 is the best rpm for max torque and economy. If you want all out economy gear it for 1750 rpm at your desired road speed, but this would be light load or unloaded.

The G56 is lower top gear than the automatic.

The rpm ranges being run on the hiway speeds are perfect for towing at the truck's capacity which is why, for the most part, they are purchased.

The higher rpms allow more air to run through the engine and the combustion chamber and EGTs are cooler which means fairly heavy output under constant conditions is acceptable.

If you put 12,000 lbs behind it you will see how perfect the gearing feels and how it is a walk in the park for this truck.


Here is something I learned with my '96 12 valve. I had a 25' GN flat deck trailer, 16,000 gvw, and a 12' 800 lb (GVW) landscaping trailer. Guess which got the better mileage towing empty? That blasted lanscaping trailer has a 5' tall tailgate sticking straight up. Even though it is mesh it is a barn door. I towed both empty over many miles. Today, I tow the landscaping trailer with an Expedition and I am still amazed at how i have to stick and keep my foot in it. Honestly, it is like a dang parachute!!!

Moral of story, do not underestimate air drag on a small trailer!!

 

Not to be a butt head, but, it sounds like a lot of the research you did was listening to your friends bragging instead any kind of real world experience. If you had driven that exact truck and asked around on these forums it would have become quite clear that a lot of people are fundging their mpg numbers.

For what you have your mileage is consistent or even a bit better than normal. Drive 60-65 mph then check your mileage again, you should see that 19-20 mpg with ease. The manual trans is made to tow heavy loads os the OD is a lot lower than is effective for 70-75 mph driving. Test driving one of these trucks first would have shown that easily.

Mileage is not bad for a trailer if your trying to hold hiway speeds on a stock truck, even a light trailer. Your pushing a big heavt truck thru the air and the way the aerodynamics are a small trailer close the truck acts like a drag. add a longer heavier trailer that is lower and mileage could actually improve.

The second big problem is you said it was stock. The engine is tuned to emissions in stock form, counter productive to efficiency. If you want good mileage get a programmer that will allow adding smaller increments of fuel and adjust the timing. That will do way more for efficeincy than anything.

You have the basis of a good truck, but, it may cost a few $$ to make it a "great" truck in all areas.

 

I find most people that claim "great fuel mileage" usually are usually embelish their #'s a bit. Realistically you're getting good numbers for what you have. Are you sure about the #'s your gasser was getting? I have a 2003 Yukon XL that gets around 9mpg towing my trailer at 60mph. It also drops speed and goes down as low as 5 on hills. My Cummins gets around 12mpg towing the same trailer at 65mph and never slows down on the hills. Slow down to a reasonable towing speed (you shouldn't be towing over 70mph, I don't care what anyone says) and your mpg's should improve.

If you wanted a loud truck that makes the turbo sing you got the wrong truck. The 3rd gens are built well and very quite compared to the earlier ones. Take out your silencer ring, gut your factory intake, and loose the muffler and it will sound nice...not to obnoxious, but noticeable.

Remember, these are big trucks with poor aerodynamics. The biggest plus is that our Cummins will be pulling just as hard and getting the same fuel mileage well past 500,000 miles. Try that with a gasser!!

 

The 5.9 gets its best mileage 2000 rpm or lower, there is a sharp drop off in mpg as you spin faster, a cliff at ~2200 rpm. When I choose to ride about 2000 rpm (about 65 mph), I routinely get 20 mpg +. I get 25 mpg driving the back roads at a steady ~45 mph. Cold weather warm ups and running the AC will eat into the mpg significantly, as well as winter and poor quality fuels.

By 2007 the G56 gearing was changed, sounds like the truck has the newer ration. I run large diameter tires as a poor man's OD on my 2006 G56 mega.

 

The advantage to a diesel is at high altitude - where a NA engine loses a lot of power - and towing heavy loads. If neither of those apply to you, then a turbo diesel is probably not the right vehicle for you.

The other big advantage used to be that diesel was the cheapest fuel you could buy. Up until about 2 years ago.

18-20 mpg is about the best you're going to get. Just like a gas engine, your driving habits affect mileage more than anything else. Hot rod one of Dodge's new Hemi engines and see what happens to the mileage.

Face it. It weighs nearly 4 tons, is about as aerodynamic as your garage, and makes over 600 ft/lbs of torque. That's gonna burn some fuel.

With the price of diesel, my next truck will be a gasser. Then I'll add a turbo to it.

 

You probably ought to consider selling the truck if running empty or pulling a 3000 lb trailer at 75 is your thing. Not a good match. And I think the 5.9 diesels are reselling for a premium price now.

I don't know how mine does at those speeds because I only get to 70 going downhill towing sometimes and then I am pretty much coasting. I run 60-65 and get 13-17 towing either a 6000 or 8000 lb trailer (about the same milage with both of them). I could get better milage towing, but I tow in tow-haul all the time. No good to save fuel and have to buy a transmission. I get about 20-22 running in the high 60's empty. Auto trans, 4 wheel drive, 3.73. About 17 in town. I get about the same fuel milage with the 6000 lb and the 8000 lb trailer. Head winds give low milage, tail winds give great milage. That tells me that wind resistance is a big factor and I think drag goes up with the cube of the speed? Or at least the square. Stopping a lot when towing really drops my milage. I stop often, every hour probably. I don't just drive like granny, I am granny.

I have been on long caravans with Yukons, and Avalanches, and other gassers. All I know is that they stop for fuel about 3 times as often as I do. And they ask ahead of each segment if there are "hills". Maybe they got little tanks? I got 9-10 pulling the smaller trailer with a 150 and I went a whole lot slower up grades. I sure like pulling with the heavy truck and the diesel better.

 

Once upon a time diesel trucks were purchased as a tool to pull loads. Mileage was an afterthought... I would say 9/10 people I talk to with mpg complaints answer "no problem" when I ask them "how's the power towing?".

And for how the original poster uses the truck, and auto equipped truck would have fit the bill much better.

 

fostert,

You're right, its a pig and doesn't run right. All it will do is cost you money and heartache. You'll throw so much money at it that you will think its an ex-wife on steroids

I will be happy to take this problem off your hands and may even kick in a few bucks so you don't feel its a total loss.

Cheer up, there are a ton of guys and gals that would be very happy with you "problems"..................all have Powerstrokes or Duramaxs

I got mine from Houston and the MPG with the "Southern" fuel was 21MPG. I filled up here in NY and I lost a tad over 3MPG. The winter blend really screws up the mileage. Try using som Opti-lube fuel additive, it will add some lubrication to the CP3 and even make the engine sound quieter. Some great stuff.

 

I didnt know that. I must have had the NV5600 in my last '03, as it too had a 3:73, and if I recall it would turn about 1700 RPM at 65-70. I now have an automatic with 3:73 gears and it turns around 1800 at 70, and gets right at 20 MPG on the highway empty. I think if the OP gets some taller tires he will see an improvement in his mileage.

I traded in an '06 F150 with the 5.4 gasser that never got over 16 MPG. I now have more truck, and it costs less to drive it. Not to mention the cool factor. I will never again stray from an oil burner!

 

Bear with me, here, if you genuinely want fuel economy in a medium-duty engined/transmissioned pickup truck (and assuming you are investigating any mechanical/electrical problems; also, what is your average speed per tank? Should be 27 mph or higher):

Do a search on fuel economy, mpg, etc, here and on other Cummins boards. Also, Ecomodder and others. You have lot's to learn: tire type, tire pressure, alignment specs, weather, climate, fuel quality, filters, onboard electrical use, are just a few. Details. The experience of others with those details. Etc.

First, it isn't to be driven like a car. Or a gasser pickup. It's slow up to speed (so what?) CUMMINS sez that the difference between the poor and the superior driver -- all other things the same -- is 30%. If you are averaging, say, 15 for all miles, then another man can get just above 20 to cover the same distance and to do the same work under the exact same conditions.

Second, how you drive is important, and, if like more than 90% of drivers out there, probably there are a lot of bad habits to break no matter the vehicle driven. Cutting the corner in an intersection, for one. Changing lanes to get around traffic instead of choosing a freeway lane and keeping it (at a better speed); accelerating before the truck is straightened out (in turning at an intersection the truck is, by law, supposed to be in line with the lane to be entered before entering it. Etc. Ton's of small things to learn and remember and practice.

Lot's of idle time, wasted short trips, (failure to achieve full warmup), and more details are killers of mpg. Your truck, your money, are either disposable or not. And if -- as with 90% of Americans -- you do not know your annual transportation costs on a cents-per-mile basis, then this is where to start. See AAA and EDMUNDS.

Third, it's heavy. That means a slower speed around town to avoid brake use. It's easy (very easy) to see who the poor drivers are based on brake use and brake life (tire life similar). I don't ever drive over the limit around town (safety issue with entering traffic), but I do drive all miles, town or country at 1,700-1,900 rpm. If that means I run 33 in a 40, so what? I just catch the fools waiting at the next stoplight, (I never stop), and then I catch them again. And again. And again.

You can also look at this as keeping manifold pressure and temps down to a low point if you want some cockpit toys.

Mopar1973Man's Notes: Keep your pyrometer under 600°F and keep your boost pressure under 5 PSI.


Bottom line is that it is heavy and slow. Let the truck tell you what it wants, and learn to listen to it. Doesn't matter a good #&$ how that makes you feel, it's where the money is, and that is what matters.

Also read threads on the NV-5600 (or G-56) and learn more about shifting. Keeping the spooling minimized -- evenly -- is smooth practice in going up through the gears. I come out of first at about 16-1700 and make other shifts 18-1900 when empty. Just let the gearshift "fall" into the next slot. Be easy and ignore what the sheeple are doing.

http://www.turbodieselregister.com/f...ml#post2182117

. . I also shift slow and deliberate. My technique is to push in the clutch, pull shifter out of gear and hold it with slight pressure in the next notch until it drops in. To me the less pressure used in going into the next gear (whether upshifting or downshifting) equals less wear on the synchronizers. Don't know if it is true but I have gone 350,000 miles on one NV5600 before the bearings wore out and the synchro's were still working good. Had them replaced anyway just because it was already torn apart.


Never give the engine power until a heartbeat or so after the clutch is fully engaged in the gear.


If you can drive this truck smoothly, never getting on the brakes or hurrying the shifts about half or more of your "problems" are over with around town.

If you want to be 2/3'rds (Zen): The throttle has no function except to move between gears.

On the road, keep speeds below 60 mph. On a 300-mile trip it's about 25-minutes longer than running 70. And you'll never change lanes, never have to worry about bumper-to-bumper, and get excellent mileage. I put the cruise on 58-mph/1,725-rpm before I'm at the end of the Interstate entrance ramp. If that makes you late leave earlier.

In other words, start over in your driving. Scratch. If you start now it'll take you about 10k miles or one year to sort your "problems" in changing habits by responding to different cues. The man is separated from the child by conscious choices . . . we start driving as children and we have the habits of children. Believe me that I would never allow anyone under 25 to drive a big truck. It takes until then for the mind to plateau. I've started over more than once due to this sort of reckoning.

If a man can't drive for economy I can guarantee he can't drive for performance. There is no difference.

Good luck

(My numbers in signature)

.

 

I like the thoughts Rednax. That is my MO when I ride the motorcycle. Make everything flow, use momentum, keep stuff smooth. That goes a LONG way for the performance of the vehicle as well as the comfort of the ride.

 

I agree... Sell the truck. You don't need a diesel and you aren't prepared for it. They have some shortfalls but many more advantages.

You may pay a few pennies more for fuel, or maybe more (I'm paying 40 cents more per gallon, or 12% more) but the engine will outlive any gasser, with less maintenance, and have significantly higher resale value, all while working much harder along the way.

If you can't appreciate the Cummins for what it is, you need to sell it.

Mileage tip: Put a Smarty jr in the truck and get 3-4 mpg more, plus more power, and fewer problems.

 

I would think your numbers are right in line for realistic driving(ie: 70 on the highways). I bought my truck new almost eight years ago, and these are close to the numbers I have seen from that time. From stock 265's to 285's to 315's, I have never seen a significant change in mileage(I presume a mix between drop in RPM/greater rotating mass canceling each other out). From stock programming to performance boxes and recently a programer, never seen much of difference. I have tried shifting at different rpm ranges, never a significant diffrence. 16-18 MPG (unloaded mix city/highway) is what I have typically seen, always hand calculated. I never expected 20's despite what I had read on any website. I don't doubt those numbers are possible at lower speeds for a 4 wheel drive, just not necessarily realistic driving.

Again, these are just my thoughts and opinions from my personal experience over the last eight years.

 

Put a gear vendors overdrive unit on it you will be turning 1950 rpm at 75 and bring fuel ecomony to 60 mph numbers. the G56 trans is not as fule efficent as the automatic but more durable

 

i have a stock '08' 3500 2x2 mega. i average 18-20 empty. i have gotten as much as 24 and as low as 17. depending on speed, weather and fuel (summer or winter).
my best mileage empty, is at 65 mph and the worse is at 80 mph.
towing i average 10-12 10k load.
usually i tow at 65...