Just "upgraded" from a 2006 2WD MegaCab 5.9l Cummins to the 2011 2WD MegaCab 6.7l Cummins. The 5.9l had a very optimistic on-board mileage calculation of up to 22mpg even towing a trailer, whereas it was really 4mpg less calculated manually at time of fill-up at the station.
The 6.7.l onboard system tends to be more accurate if not a bit pessimistic showing a fuel mileage of around 13-15mpg, where it is actually more like 14-16mpg.
Bottom line is though that my 6.7.l Cummins needs more Diesel, even though I am driving quiet conservative, partially due to the fact that I have only had the opportunity to put roughly 2000 miles on the truck in the 3 month of ownership.
Coming from bone stock, does anybody have any proven suggestions on how to take reasonable measures improving the mileage without compromising the warranty or at least without altering the truck too much without being able to build it back without great effort?
F.y.i. I am from CA, we will have smog issues here, truck is supposed to be equipped with equipment to pass upcoming Diesel smog laws.

 

the only thing you can really do is get a programmer, and turn off the egr and the dpf, but you have to delete the dpf if you turn it off, for most, doing that has netted mpg's up in the 20's...

 

What programmer hardware/software will do the job? Are those mods reversable in order not to affect the warranty.
What about any intake mods, as far as getting more air into the system?

 

You can't really have it both ways. Either you have your warranty and emissions equipment intact, or you have better fuel economy and power.

 

R_D: Be patient. The mileage on my '08 2500 Maxi Cummins didn't start to get good until after I hit 10K. I didn't mind. The tighter tolerances of the engine will help it last longer. Mileage has steadily increased with the miles on the truck and now, at 20K, I'm getting 12+MPG pulling my mini excavator (about 15k #'s) around town to jobs, and just this week got nearly 22 MPG on a 6 hour trip with about 3/4's of a ton on the truck. Get some miles on the truck, leave the programming alone (Daimler did a great job of applying the Bluetec diesel technology to the Cummins), and the Allison 6 speed works flawlessly to match engine speed and load. Mileage that far exceeds any hint of an EPA rating is coming your way. I absolutely love this truck. I've had many trucks in my 40+ years of construction - this is the quietest, best riding and handling, most fuel efficient one I've ever had. The family votes to take the Maxi on all family trips, and I don't mind 'cause I love driving it. The stereo kicks A$$ too.
By the way, to answer another question: My dealership, Greenbrier Dodge, offers synthetic oil changes for the Cummins. Unfortunately, I can't afford to have them do it for me, but I use a major brand that has both Cummins and Dodge approval for warranty coverage. It may help with my incredible fuel mileage, but I can't verify that. I've been using it since my first oil & filter change at 4K, so I don't have a before and after difference to compare, and that comparison would be flawed because of the low mileage on the truck. Maybe at 30K I'll try a load of conventional oil and compare and repost, buuuut, maybe not! I like things the way they are.

 

QinVA - you don't have an Allison transmission, unless it's something you hobbled together after buying it.

My truck (08) got about 15 mpg on the freeway, empty, at 70ish mph with 45k miles on it. After deleting the EGR (which is HORRIBLE for your engine) and DPF, I'm getting better than that as a combined city commute. My truck also runs the 1/4 mile in 13 seconds without much effort.

I will be switching to synthetic oil sometime down the road, probably at my next oil change, ~70k or so.

 

No, I didn't put an Allison in. I have the 68RFE. I just got confused, because I traded a GMC 2500 DuraMax(with an Allison) on the Dodge. The 2 tranny's have similar features, and work alike, but the 68 is better imo. I don't particularly care for the soft shifts at low speed/low load, where the RPM's slowly decrease. Reminds me of the old days when a tran.'s bands were going bad. But, the 68 doesn't use bands so I guess it's OK. I'm just conditioned to that being a symptom of something being wrong.
I don't get your mileage. Mine was low until just over 10k and it has steadily improved. I got 21.8 on my last trip (320 miles) and much of it was at 75 mph. That was with 4 people and luggage, AC on the whole time, and almost a ton in the back.

 

horatio102, I just thought of something. Have you had your computer program updated by the dealer? I had 2 recalls for a complete replacement download of the programming on the PCM, and it did improve things. They told me at the dealership that they had to format the PCM, removing the program and download a whole new program profile. And, they did it twice in less than 6 months. It took a while each time. They said they had to connect to the factory and have it done through a website there. Hope that part's not BS, but whatever, it did make improvements, and I did have to wait for some time while it was hooked up.

 

The updates they did had to do with allowing DPF regens at idle amongst other things to make the EGR and DPF systems a little less troublesome, as they were getting a LOT of flack from guys who were getting EGR, DPF, turbos, and other stuff replaced frequently from idling.

I haven't had mine updated by the dealership, but the assistant service manager ran my VIN and told me there are no outstanding recalls or updates for it. Not that I would have it updated at the dealer anyway - I've removed all of the emissions equipment and that's a headache I don't want to deal with.

Going back to your tranny, it really shouldn't be shifting so softly that it feels like something is slipping. You're right, there are no bands in these... so it's just clutches. The 68RFE tech over at SunCoast Converters told me the other day that they've been seeing complaints of repeated overdrive clutch failures and it's due to something in the valve body that gets corrected by replacing the whole valve body - so much in fact that their rebuild kits no longer come with valve body plates and springs/seals, they're selling the kits with complete, brand new valve bodies.

Anyway, I've had mine torn apart 3 times now and I'm loving it once more. I really liked the programing of the H&S Overdrive software, but it's not compatible with the Suncoast tranny.

 

Thanks for all the posts to my initial inquiry.
What is a proven good programmer, where can I get it, what costs may I expect.
What is the EGR, what is the DPF. What do they do, or what are they supposed to do, and what will happen/change once modified or removed other than the possibility of mileage increase?
Can the removal of the DPF be reversed?
Truck has now app. 9kmls on it, no improvement on diesel mileage from driving yet.