So I bought a new 06 dodge 5.9L Turbo. Who wouldn't? Its an everyday driver. With the truck stock, I was getting 19.5-20.2 MPG. I put around 15K miles on it and installed an AFE full air intake. I lost 1MPG. At around 36k, I bought and installed a bully dog triple programmer. I lost another 1.5-2MPG depending on the tune installed. At 82K I upgraded to a full 5" turbo back exhaust system. I lost another 2MPG.
I understood that letting these diesels breath would increase HP and MPG. I understood that installing a bully dog "should" increase MPG. I understood that not causing back pressure would not hurt MPG but could increase.
Why did this whole truck turn against me in MPG. I don't faithfully check my mileage. I get what I get, but I kept track of miles for the first 10 tanks when it was new and I rechecked 3 times after each change.
I went from 19.5-20.2 to 14.5.
I have recently removed and clean the IAT sensor. I was expecting a white sensor. My was still black after I sprayed it down. That didn't improve anything.
I have been running home made biodiesel since 28k to current during the summer, but I doubt that has anything to do with it. I keep losing MPG after I started following advice hoping to get the most MPG out of a everyday driving truck.

I had plans on installing a FASS system, Bank etc intake and some day upgrading the turbo, but with all my lost in MPG, I will be driving around a truck getting 8MPG before I'm done doing the things I thought would INCREASE MPG. I just can't see dumping more into this truck to lose MPG when I'm on a sinking ship.

Does anybody have any thoughts on what could be causing my problem?
I drive 55-60 all the time. I never abuse my stuff - AKA not on the throttle. My truck has never seen over 3.1RPM. It would be lucky to see 2.5RPM once every 6 months.

SOMEBODY HELP ME KEPT MY FAITH IN THESE CUMMINS 5.9L!!!

 

I read enough forums to try the clean out. With 86k I removed the fuel filter (just changed last night) put a rag down in the housing and cleaned it out good. I filled the filter housing full with power service and reinstalled the new fuel filter. The truck was running good until I got it across town and it started having a rough idle and rough band from 950-1250. I read tons of forums stating this would help give a strong clean for the injectors. I'm going to get it out on the road here shortly and give it a good run. I hope this helps.

If anybody else has any ideas - please reply.

 

no issues here 'cept the abs and brake light lit up 500 miles from home last week-sceered the chit outa me--i hear it's common with these trucks-still bone stock

 

What does having your brake light lit up have to do with my issues and what are you saying is common for these trucks.

It's late, but i'm lost.

 

I can understand losing mileage because of the exhaust - it's overkill for your driving habits and setup.

However, the rest of it? Seems odd that you'd have lost that much mileage.

 

A full 5" or 4" shouldn't really make the fuel mileage drop really. I plain to do some more work to this truck and with all the upgrades in mind, 5" would be the correct size for HP rating.
On the rest of the MPG lost - anybody guess is as good as mine.

I did do the fuel housing clean and dumped Power Service in the housing to the top and replaced the filter (thinking maybe a good injector cleaning). It's windy here now 25-40 MPH. I will do some checking after the wind is gone for MPG again and see if that helped.
The truck started running good again after about 5 miles.
They truck has always ran like a tank/rocket, but I was told the more miles you put on from a new diesel, the better it would get. Umm..how so?

 

A few months of tanks and my mileage is currently running around 15.5-16.8. Now I'm back on Biofuel so I have not bothered checking.

 

so let me see if i understand this. you got 20 mpg stock, you changed to some aftermarket components and lost mileage and you lost faith in the CTD? hmmmm.....

its common to see a loss of fuel economy with a cold air intake. more air equals more fuel dumped, cooler air is more dense equals more fuel dumped.

most people i saw come in the dealership with a bully dog talked about real seat of the pants power gains but at a small loss of fuel economy.

so i'm not that surprised that you lost some mpgs, a little more than the norm i think, but a loss is normal.

 

Then I think these people at AFE and bullydog should be shot because both companies advertise GPM gain. AFE claims that you open up the air system and let the engine breath you get a smoother running motor and 1-2GPM gain. Bullydog says better timing 'can' increase GPM to 2-5MPG.

I guess I should just uninstall my programmer and let my air filter plug up. Less air = better MPG I guess.

 

Maybe throw back in a dirty fuel filter? Less Fuel dump....