Ok guys, here's the info on my trucl

2004.5 4x4 48RE 3.73's bone stock, 32,000miles

I replaced the fuel filter at 15,000, and again at 30,000.
Oil changes every 7500 miles
Air Filter when needed

When the truck had 10k-28k miles, I could pull 20mpg on the highway with relative ease, as long as I kept my foot out of it.

Now, I have trouble keeping 18mpg. I did put a leveling kit on it, which may cause more wind...but I had the mileage problems PRIOR to doing the leveling kit. The tires are stock still.

This weekend, I towed a suzuki samurai on a trailer about 600miles. I could only get 11.5mpg . I was going 65mph-70mph, on relatively flat land from San Antonio, TX to Biloxi, MS

On the ride home, I had an empty trailer, and could only manage 11.4mpg...same speeds, same roads.

Any ideas what could be going wrong here? I run stanadyne powerclean through it every couple of tanks of fuel, but not in every tank.

I bought this truck because I figured it would help me while towing, saving me some fuel opposed to my old 4.7L. I was getting the same mileage while towing in my 4.7L, what gives?

Any recommendations?

Anything I should ask the dealer about?

This is the first long haul I've done with it, 1200miles round trip. Usually I tow my boat about 40miles, and I can keep it at 15mpg or so. My boat weight about the same as the samurai and trailer.

Thanks
Shawn

 

I have an 05 2500 that has about 10k miles on it and since it was new the best hand calculated mpg was about 18. I decided to go to the dealer and get the reflash for the mpg and smoke and now im getting 16 to 16.5. I just cant undserstand it. i know its a big truck but maybe when it breaks in it will do better. I would not have gotten the reflash if i could do it over.

 

I am pleased with the mileage unloaded. For a 2500 pickup, it gets better mileage, by far, than my 4.7L regular cab dodge got.

However, I expected better while towing. 600ft/lbs of torque at the flywheel should do a lot better than the 275ft/lbs I had in my gasser..

Thinking about it a little different now, I have concluded that the cold weather coupled with my 'short' work commute is probably hurting my mileage from home to work. The truck just finally 'warms up' as I shut it off in my work parking lot. From what I can tell, the mileage suffers when cold...and It is cold 90% of my drive to and from work...especially to work, as it is generally warm on the way home.

However, towing a flatbed 20' trailer shouldn't knock my mileage down to 11.3mpg, that seems horrible for such a minimal load.

And I still can't understand why I got BETTER mileage with a loaded trailer than with an empty trailer...

 

I have the same truck as you and have not figured out the milage thing yet. I started a thread a while ago about my milage if you wat to look for it. I think when you are pulling some weight on a flat roads the turbo is always putting out boost (more relative to empty) and that is what sucks down the mileage.

I get about 10-12 towing a 24' toyhauler, that is at about 63mph. Anything faster and it drinks fuel. 14-18+ empty.

 

Are you saying the boost pulls down the mileage?

I am spooling a lot more WITH the load in the trailer, and it got BETTER mileage. I actually had it up over 13mpg for the longest time, until we hit a lot of wind/rain/traffic.

On the way home, the trailer was empty, clear weather (slight fog in the morning), and no traffic...11.3mpg, go figure.

I was pulling 65-75mph loaded and unloaded, 65 up hills, 75 down them, 70 on the flat parts.

Either way...it's got the power to pull anything 70mph+ with ease...I just expected it to get better mileage while it did it. The old 2nd gen 24V cummins owners always say "same MPG loaded or not"...all talk or are the 600's that much worse?

SQ

 

I am saying I don't know why but it always seems I get lower milage when it is flat........why, I am not sure.

 

serves some of you guys right that you got the reflash expecting MORE then 18mpg's and are now getting what most others are

 

Yeah I have been avoiding the reflash, kinda hate the thought of having to take it in for something and them flashing the thing. My mileage ain't bad just not what the older trucks get. It tows what I got no problem so I am not to upset.

 

The one thing that I have found that affects fuel milage is the direction the wind is blowing. ( my truck is not even bothered by a good stiff head wind) I know that because the truck has so much power,that we seem to think that the truck is allways going to run the same. The winter fuel and temps are bad on our diesel trucks. There is one other thing that I think mite be a little diff. in some of these mpg woes. Is if you can add fuel additives and get better milage. What's saying that all the fuel you are bying at differant places has the same cetane level. There for dropping your milage. Right now in the winter. My truck never gets the same milage. It is very inconsistant.Just a thought.

 

Your mileage does seem pretty low, is your trailer a dual axle?
I would check the pressure in the truck and trailer tires.
Is it possible that the brakes on the trailer are dragging a bit?

Tire pressure seems to be a big factor with these trucks. I noticed about 1.5mpg improvement going from 45psi to 65psi.
I would recommend changing your drive axles to a premimum muti viscosity synthetic lube, this really helps in cold weather.

Most of my trips are about 250 miles going from sea level to 3000 feet with 2 4500 foot passes, and some long 6% grades. My dual axle trailer weighs about 2K empty and has 235R X 16 load range E tires. If I run 60 with the flatbed empty I will get about 18. I did very carefully align the axles on the trailer when I assembled it and run the tires on it at 70psi to minimize rolling resistance.

I have been able to get my MPG down to 12 pulling my 27' pontoon boat. It weighs about 6500 on the trailer and has allot of wind resistance. The boat has a fixed hard top that is about 13 feet from the ground when on the trailer. With the pontoon boat on behind I have to apply throttle to maintain 65 on a 6% downhill grade!

Regards,
Jim B

 

I don't know how windy it has been down in San Anton' but up here along the border it has been one windy son of a gun for the past 2 months. We have had very few calm days all winter and that has hurt my fuel mileage. yesterday for example the overhead showed 20.1 on the start of my 45 mile one way commute and by the time I was half way home at about 1o'clock it was already down to 19.9 so that is something to think about.

 

It was definitely windy...but it was equally windy both ways, there and back, so I assumed it wouldn't effect mileage (and from the same direction, out of the south, which blew the wind perpendicular to my truck (I was traveling on I-10 East & West), so it shouldn't have made a difference.

I don't think my tires are at 65psi, even though the $tealer$hip said they check them when I get my oil change (free for first year!).

I can't find a gas station around here that has a pump that will put 65psi into them either...doh!

SQ

 

You don't check your own tire air pressure? Filling station guages are notoriously inaccurate. Buy yourself a good quality air pressure guage. Digital is easier to read and use. Sears has nice little air compressors on sale often for $100. They are quite useful for other things like blowing up pool floats, basketballs, etc. Low tire pressure is very common in the American motoring public. I often see cars with one or more tires half flat. Awfull on mileage, both gas and tire.

My truck has recently been getting a consistent 21.1 mpg. That's running empty with front at 55 and rear at 45.

 

trip there might also be the fact that the thing you were towing is a block, not exactly the most aerodynamic thing to tow, but that doesn't help for the return trip; also if you got bad fuel on you departure. I went to Lincoln NE from here and averaged 23.1 on o/h and 23.0 hand calc, on way back same thing, but stopped to get low priced diesel in OKC and it fell to 9.8, checked filter, NASTY, drained tank, had lines flushed, back to normal Just a thought

 

I believe you are correct to believe there is something wrong with your Cummins. I just completed a 2500 mile trip, Wyoming to Yuma, AZ, encountering all kinds of driving conditions and averaged 20.4 hand calculated. (19.9 on the overhead) My Cousin drives an 04.5 2wd dually with 4.10's and gets 11-14 pulling a 34ft 5th wheel.
Both of us drive conservatively, keeping rpm's under 2000.
Having said that, I believe not all Dodge Cummin's are equal and can't explain how people with similar driving habits report fuel economy numbers all over the page. Are your diesel specs out of whack, pump, valves, etc? I think it is worth a trip to your dealer to check it out, or to a private diesel mechanic who has a strong diagnostic reputation.

Good luck!