E-mail from Cummins on the 04.5 mpg issue

[doldenburg]

this seems to be a 04. 5 600 problem. you guys telling us how good your 03 trucks mileage is does not help. we know older trucks do better , thats why we are whineing.

 

[bzingre]

Alright, we are forgetting something

for a 98% reduction in NOx, there is going to be an efficiency loss. Cummins and DC added a cat to the 600, but the cat alone did not provide the full reduction in emissions. The post injection does not increase combustion temp, but rather aids in keeping peak combustion temps low (high combustion temps increase NOx formation). Also, I'm sure that timing is retarded in most operating conditions to help meet emissions (again, lower combustion temps, but higher component temps). So that means that in order to maintain or increase hp, there needs to be more fuel.



We should also feel lucky that Cummins was able comply without EGR on ISBe, that would be worse. EGR decreases volumetric efficiency and causes an even greater decrease in fuel economy, not to mention sulfuric acid formation in the combustion chamber.



I'm not saying that I know all this for fact, but what I am hearing is low fuel complaints, so looking at what has changed (cat and + 20 hp/45 lbft. ) there leaves the above options as possibilities.

 

[Mopar_Mudder]

Well I got to drive dads new 2500 with an auto and 4. 10's, yes the new 600



it has 800 miles on it and the overhead say 14. 5. This is all mainly around town driving, no crusin down the freeway. I would say that is right on the money for only 800 miles.



I know that the compture may not be dead on but they are very close. The computer in my 03 was within 0. 1 mpg before I put the EZ on it.

 

[geusterman]

My 02 4x4 6spd was a major disappointment when I bought it... sometimes 12mpg... to 14mpg. When I sold it at 22K it was just over 18 and over 19 with the EZ. My new 600 yesterday at 4400 miles was 14. 6mpg with 2/3 being town and a few burnouts. I think I am going to be content here and let the 600 get some tow miles and keep my eye on what the box boys do. I bet new 04's with autos and 4x4 like mine did not see much difference when new. George

 

[RobbieH]

Originally posted by doldenburg

this seems to be a 04. 5 600 problem. you guys telling us how good your 03 trucks mileage is does not help. we know older trucks do better , thats why we are whineing.

The thing is though, most the whining is coming from people with far less than 10,000 miles on their trucks. I wonder why they have that sign hanging in your new truck that says don't ***** about mileage until broken in, and that break-in can take 30,000 miles... I'd say judging by that alone this must be a common complaint when people get their first new diesel.

 

[JWerkheiser]

OK, to those who say we can't complain since our trucks aren't broken in yet, How do you explain the fact that my '03 off the lot got 5 mpg better than the 04. 5 I just got? Since the only variable is the engine change, I am concluding that the 04. 5 costs 5 mpg. 22. 3% drop in mileage for 6. 5% more horsepower, and the emissions garbage. Oh, and I forgot, the leather seats. Probably around 2 mpg there, right? Not a tradeoff I like, but since Dodge forced me out of my other truck, I had no choice.

 

[RobbieH]

Most the complaints I have seen have been around 16-18 mpg. That's what my '03 HO did out of the box too, and did for a long time. Mine's going to do a little better MPG wise than an auto or a 4x4 too, so those have to be taken into consideration.



I agree if you are getting 8 MPG, that's a problem, but 15 MPG in a 4x4 auto dually isn't bad at all.

 

[Apence]

I think alot of people are complaining arent first time diesel owners and have experienced the increase in mileage after break in but we also didnt start of at 12 mpg and see 18 after 10 or 15k miles. I have worked mine since it had 500 miles , I tow a 24,500 pound gooseneck all around town most days of the week, I now have 2800 miles on my truck and up to 14mpg empty I now its not broken in yet but trust me towing that around works the engine really hard and is probably equal to about 10k miles of easy driving. My 95 towed nearly as well and got 19 same fuel same driving(empty). we bought theese trucks thinking that they we as good as the previous 2003 and 2004 cummins motor with what dodge and cummins says are some minor improvements, however this being my third cummins Iam not very impressed with this 600 so far. combination of bad mileage and doesnt tow any beter than a 95 175 horse model with a 5speed. Im sure there are some great 600's out there that are getting 18mpg and have great power but some of us arent seeing the power or mpg so there must be some problem with some of these 600's. and it has been to the dealer twice for reflash. Post reflash slight loss in power 1/2 mpg increase. I have one question to, I run the stratapor filter and rotella T and my oil is jet black within a few hundred miles is that the way most of the 600's are? My 95 would stay clean till about 5000 miles. I also have poor start up with white smoke and rough idle even at 70 degrees. That is why I think there is a problem with the truck, however been to dealer twice and they say it is fine.

 

[RobbieH]

My '03 gets black pretty fast, and I'm using the same oil and filter.

 

[David Oxland]

It sems to me that wishing for EGR is thinking that the grass is greener on the other side except that it isn't; it's blacker.

A month ago I went to a lube conference and there were quite of few Bus maintainers there who used to operate with 12000 mi LO changes. Since EGR has been fitted to the new buses they purchased they are down to 3000 mi changes and when they pull an engine it's full of **** in the sump. Feeding exhaust gas back in tends to make them fill up with dirt! They were really crying the blues.



David

 

[jlasich]

Apence, if you're still having problems after the reflash, then I'd say yes you do have a different problem. Check out these this thread from someone who had the same similar problems to yours.



http://www.dieseltruckresource.com/dev/showthread.php?s=&threadid=41216

 

[Apence]

thanks JLasich

 

[doldenburg]

RobbieH- this is not my first diesel. my 1st was a 88 ford 7. 3 non turbo-good truck but short on power with much better mileage than the gassers i had been driveing. Since then a 93,98,01,04. 5 all dodge. i went to dodge for the cummins. my 01 3500 work truck with tools and towing a compressor loaded to around 16,000 lbs does as good or better on fuel. i have been driveing pickups long before it was cool.