Greetings,

I've got a 06 CRD that when I initially bought it got great gas mileage. After going through all of DC super fixes, the mileage took a serious nose dive. I went from being able to get 27 mpg in a mix of city/highway to only 22 mpg even if it was 90% highway. After following this board and a lot of experimenting, (unplug this, plug that in) I have finally been able to start getting the mileage to go back up. I've done the orm. I check the boost sensor on occasion to make sure it stays clean. I've had my ECM tuned by inmotion (stage II). I tried a lift pump for a short while, but I removed it as I think the pump could not keep up with the flow requirements. All of these things have made drivability a lot nicer but here is the kicker.

I still have the stock airbox and an amsoil air filter. I removed the inlet tube between the box and the grille to see what would happen. Drivability remained about the same but my mileage went up 4 mpg. If I put the inlet tube back on, mileage goes back down. So off the tube comes. To further the experiment, I took the airbox out, fixed the air filter to the lid and hooked the lid up to the turbo intake hose. Now for the test drive.
Here is what I noted:

1. Engine noise was significantly quieter.
2. Acceleration was greatly improved. You could definitely feel the pull.
3. I'll be watching fuel mileage to see what happens.

It's like an entirely different jeep. I know some people have swapped their airbox out for one from a 2002 liberty and I may try that. However, I’ve seen a couple of threads pop up lately where people have had their turbo replaced. Is there a simple way to tell if the turbo is headed for the trash heap?

I do not have any mods to the CCV, though I am trying to figure out how to fit a racor ccv4500. I know one other member tried, but failure is not an option.

Thanks & Merry Christmas

That's neat info about the air intake, keep us posted on milage, I would think it should go up if you're driving it the same. I had my turbo replaced under warranty along with a lot of other guesswork on the dealer's part, but they said the actuator for the variable turbo had siezed. They had to replace the catalytic converter also because after they replaced the turbo it was still throwing a high boost code (which was the reason they replaced the turbo). I really think there was nothing wrong with the turbo. Tigafila

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'05 CRD Limited: 174k mi Euro Torque Converter, EHM, ORM, Racor fuel filter, Original Rocker Arms, Amsoil everywhere
'98 Dodge Ram 2500 Cummins 24 valve extended cab short bed
'01 Jinma 4wd diesel tractor

This is our situation to a T. I am wondering how much the Inmotion tune has hurt us, as I don't think we've had a tank with good mileage since the tune was done. Of course, we had taken two trips with our camping trailer at that same time, and then we also put load range D tires on, and that's about when the weather started to get cold, and not long after that we had a defective CCV filter replaced, then the turbo was just replaced due to the excessive oil (and soot) in the intake. This made it somewhat difficult to nail down the cause to any one specific change...

- Chris

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Used to own:
2006 CRD Sport
Suncoast TC, Transgo shift kit, Inmotion, ORM, EHM, Magnaflow SS exhaust, Fumoto valve, EVIC added, Hensley TruControl brake controller, Pirelli Scorpion ATR LR-D in spring/summer/fall, FIA winter front and Blizzaks in winter

You might also have been caught in the change to "winterized" #2 fuel. That's good for a 2-3 mpg drop.....more if pulling hard.

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2006 Libery Sport CRD, Lt Kakhi, nicely equipped
*****GDE Hot Tune at 38,879 miles
*****Stock TC.....for the time being!!

Winterized fuel and extra weight of the cold air might do that yes.

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L.O.S.T forever!
Silver 2002 Skoda Fabia TDI, 235,000km
Former car: Jeep KJ 2003 CRD

DIESEL - saving millions of liters of petrol every day!

Fuel quality makes a HUGE difference in mileage. Thank goodness we don't get "winterized" fuel here in Tennessee, but even running #2 from various stations, one tank will give me excellent mileage, the next not so good.

In a recent trip where I was towing my trailer, I got 25.1mpg one way, and coming back only got 22mpg. This was all highway miles.

Not towing, I've seen as high as 30.1mpg and as low as 26mpg on the same trip. I typically use the cruise control as much as possible and try to keep my speed around 70-75mph.

If I get lower quality fuel the exhaust smells worse too. I call it "skunky" fuel. Stinks like crap when I get out of my Jeep. Good fuel really has no smell to it. I have also run a tank of biodiesel and it's the BEST. It actually smells "clean".

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Chad Hargis
Nashville, TN
2008 Grand Cherokee CRD
2005 Liberty CRD *SOLD*

If you can borrow a Scangauge II you can visually check at least two things that might be important to know.

1. Boost Pressure (MAP on the Scangauge II). This will tell you if your turbo is making boost at appropriate levels. This MAP reading is in psi - and is absolute pressure - meaning that it will read (without engine actually running) somewhere shy of 14.7 psi (atmospheric pressure) depending on how high you are above sea level. With the engine running, the MAP will vary between 14.x and roughly as high as 34 psi (which translates to approx 20 psi of maximum boost). If you have installed aftermarket performance logic, the maximum boost might be higher.

2. The IAT (Intake Air Temp) is the temperature of the intake air charge at the manifold. This reading comes from the same MAP sensor module. With orm invoked, this will generally be 35-45F or so warmer than ambient air temperature. I suppose this is due to the compression of the air charge by the turbo as well as heat absorbed from the turbo itself and by the intercooler and air plumbing under the hood. If the orm is not being used you can count on the EGR to raise the intake air temp by at least another 35-45F. With the SGII you can at least verify when the EGR is adding heat (exhaust) to the intake air charge. Something that might be helpful to know when evaluating effectiveness of the orm.

The downside to the Scanguage II is that on our precious Jeep Liberty CRD the OBDII data will often stop responding to the gauge after a random interval of time. Mine varies from a few minutes to as much as an hour or so. Setting the gauge RATE to SLOW or NORMAL will help stave off this gauge lockup issue but in my experience it won't entirely eliminate the potential for it to happen. Apparently the data response problem is in the CRD computer implementation and not the SGII. I have no idea as to how we might convince Chrysler/Jeep to fix this - but it sure would be nice if they would. I have purchased and tried a DashDyno SPD that behaves similarly in this regard.

Good luck with your mileage quest. Keep us informed.