Poor Diesel Mileage(Dodge)

[TOMLESCOEQUIP]

I'm now on my 3rd dodge diesel pickup, my first being a '95 model that got a consistent 20.5 mpg, the 2nd a 2002 that averaged between17.5 and 19 mpg, and now a 2004.5 that gets about 13 empty and 10.9 loaded pulling around a 7000# load. All trucks are automatic transmissions. Although I'm impressed with the power of the new "quiet" Cummins, the fuel mileage sucks. The best I've ever gotten with the new truck is about 16 mpg on a long trip to Canada. With the price of diesel going ballistic, I'm looking for any input on improving the mileage. Does anyone have any experience with the multitude of boxes and gadgets available........Any mileage increases to be had with these devices ?? How much can be done to these trucks without voiding the warranty ?? Can I install another exhaust system with less back pressure for any increase in mileage ?? ( I really don't want to go really loud........sort of defeats the purpose of the "quiet" Diesel !!) The truck has great power, and one would think that the mileage would be alot better than with the old mechanical injection since the computerized injection became the standard..........Why does it seem like mileage is regressing as technology increases ?? .........Tom

 

[cowboydoc]

<font color="green">Why does it seem like mileage is regressing as technology increases ?? </font>

That's a pretty easy one. They have about doulbed the hp and torque from your 95. Plus you would have seen a couple mile/gallon increase over the slush box autos that are put behind that beast of a motor. Why dodge hasn't gone to a five speed transmission I have no idea. Ford and Chevy are going to 6 speed autos and dodge is still on the 4 speed.

As far as what to do about the mileage I watch the TDR site quite a bit. The add-ons from what they are saying aren't helping very much with mileage. Good increases in power but mileage sucks. Also with any aftermarket part you run the risk of your warranty being voided. On that site quite a few guys have run into problems. Plus depending on where you are at if you change the exhaust you may not pass emissions. Even under the best of circumstances even a free flowing exhaust would probably only net you 1 mpg. But depending on who you listen to and believe there are some guys claiming the newer trucks rely on the backpressure to run cleaner and combust the exhaust more fully. This leads to less fuel being burned so some are saying your mileage will actually go down. /forums/images/graemlins/confused.gif

I was extremely happy when Ford came out with their new truck and Dodge is right there too. All the stuff we used to do, bigger exhaust, intercoolers, higher hp, etc. is now done on the trucks from the factory. My current 6.0 runs like my 7.3 did with all the mods. I have been really happy with Ford. That's not to say I wouldn't have liked to have had a Cummins with a 6 speed manual though!!

 

[RobertN]

What else is different about the trucks? Did you go from 3.55 gears in the old trucks to 4.11's in the new one.

Low gears and automatics take a hit for fuel mileage. Bigger tires?

My '01 2500 4x4 auto with 4.11's actually got 18mpg on a trip two weekends ago, on the open highway. Usually here in the foothills, I get 14 empty(that's not with particularily thrifty driving habits).

My buddy with the same truck, similar driving habits, but with a 6-spd stick and 3.55 gears gets lot better mileage than me...

It sounds, from the very brief description, that you may have lower gears in this truck. Otherwise, there is most likely some issue going on.

 

[TOMLESCOEQUIP]

The new truck has 3.73 gears. the 02 had 3.54.........as did the '95. I thought the 95 was a towing horse compared to the big block chevy's I'd had previously........Then the 02..........What an animal !! The new cummins in the 04.5 is an even stronger puller........I know the power is up but didn't they re-do their auto trans to a complete new design since the '95 ?? ( stronger-more efficient ?? ) Also the '95 smoked like a freight train and still got good mileage.......The new truck hardly smokes on the road and very little at start-up. The stock tires on the 04.5 are also taller than the 95's tires were..............Shouldn't that make up the gap in the gear ratio ?? I'd buy another "new" 95 if I could get one !!

 

[cowboydoc]

The transmission is kind of like when ford went from the E to the 4R100. Yea they beefed it up some but it was still basically the same no good tranny for a diesel transmission. That's basically what Dodge did. It's not just you on the new dodges. Go over to TDR and they have been having a fit about the mileage for quite awhile.

The black smoke you really don't want. The more black smoke indicates more unburned fuel, ie wasted fuel. The newer trucks have to meet much stricter emission standards. It is this reason that the new trucks are SUPPOSED to be getting better mileage because all the fuel is burned and the there is very little exhaust. That is the ONLY reason that Dodge went the way they did and Ford couldn't keep the 7.3 anymore because they couldn't meet emissions as they were.

Fortunately Ford got it somewhat right as the mileage with them has gone up some over my 7.3 and that is with the 325 hp and 600lbs. of torque. Dodge still needs to get the mileage part figured out. Somewhere in the design they have lost significant mileage and as of yet they haven't been able to figure out why.

Unloaded your gears will make a little difference. On a like truck it makes 1-1.5 mpg difference. Towing I've found I actually will get worse mileage with the heavy loads as the truck is shifting out of overdrive much more.

 

[budman72]

Tom,

I was lucky and found an 04 555 instead of a 04.5 600, my mileage is about 18 combined, if I keep it under 2000 rpm I can get over 20.

Check on Dieseltruckresource.com - it looks like there is a software upgrade that might help the mileage.

As far as Dodge's 4 speed tranny vs Ford & GM's 5 speed, the Cummins has a real flat torque curve, the V8 design of the others peaks out more at high RPMs. They need the extra gear to stay in the power range. The 4th gear in the Dodge is about the same as the 5th gear in the others.

 

[LarryRB]

My HO 01 with six speed gets over 20. I would think the automatic is the biggest problem..

 

[cowboydoc]

<font color="green">They need the extra gear to stay in the power range. The 4th gear in the Dodge is about the same as the 5th gear in the others.
</font>

Yes you are right high gear is the same but it's getting to high gear that is the challenge. Also if the cummins doesn't need the extra then why did Dodge go to a six speed manual instead of just staying with a five speed manual? My opinion is that it does matter and with a diesel you are much better off with a five speed auto than a four speed auto. There is way too big of a jump between gears. Not towing doesn't matter but towing it makes a huge difference and again I ask why did Dodge go to a six speed manual if it makes no difference?

 

[NIXON]

Didn't Dodge go over to the 48RE auto trans ? For some reason I got the impression it was a 5 speed and very robust . John

 

[QueBota]

Tom,

I sent you a PM.

Dave