Bad milage...what could be wrong?

arbby · **Joined:** Thu Oct 18, 2012 6:22 pm **Posts:** 27

Hi all, new to the forum not to Jeeps (2 wranglers and a TJ).

I have a 2006 KJ CRD, 230 KM

I have done the EHM, ORM and cleaned the MAP sensor, new air filter, 192F Stant inline thermostat and new fuel filter.

I only get apx 20 mpg highway.

I have stock size tires and stock otherwise and automatic.

What could be an issue and where to start.

Synthetic oil change in the next few weeks.

Thanks all.

jeepdan · **Posted:** Wed Nov 14, 2012 1:53 am

First thing I would do is check for dragging brakes. Also feel the rear wheels for excessive heat after a drive, which will indicate the parking brake is not releasing. I had this problem with both of my libertys. It made a very noticable difference in MPG.

kapalczynski · **Posted:** Wed Nov 14, 2012 2:59 am

Where is your needle for your engine temperature sitting at? It should be just a bit below half on the gauge. A common/likely issue is the thermostat going out on the KJ CRD's.

Diesels are much more efficient at operating temperature than at lower temps so a bad thermostat would hurt fuel economy. The CRD also has a heat generating pump (I forget what it's called but from my understanding it basically churns silicon to create heat that warms the coolant as it passes by) to assist at getting the vehicle up to operating temperature. If your thermostat is failed open this would also be fully engaged all the time causing extra load on the engine and further driving down fuel economy.

Another thing to check is on my previous CRD KJ I had a small leak in the intercooler. This obviously causes the turbo to generate more boost that the map sensor thinks it has and it also causes the boost to bleed off/surge and become unstable as it tries to maintain the expected amount of boost. This too can degrade fuel economy. This I would imagine would be a uncommon issue, but thought it was worth mentioning since it happened to me on a factory original intercooler that was defective.

Hope this helps get you started,

Good luck!

RJM · **Posted:** Wed Nov 14, 2012 9:03 am

I see that you posted your mileage in km so I will assume you are from Canada. 20mpg is not out of the ordinary with our crappy winter fuel and cold weather. I expect to take a 25% hit in mileage in the winter with my CRD resulting in 22-25mpg at best. Over the last 6 years I have been blending with #2 or bio to boost mileage, just be prepared if the weather takes a nosedive. Also good to check the things above anyway. :2cents:

dirtmover · **Posted:** Wed Nov 14, 2012 9:29 am

+1 on what RJM says. Check out my fuelly for data to back up his seasonal variation comment.

There's maybe nothing wrong!

Is this CRD new to you? If not, what mileage were you getting before?

If it is new, where do you live? Where do you do most of your driving? What is your driving style. Depending on the answers to these questions your may be typical e.g. if you live in one of the Northern states or Canada and dive mostly city then 20mpg is probably about right.

If you bought expecting the 30+ that some report then you're going to be disappointed because these numbers are only achievable when driving under very specific conditions which include 100% highway and driving like a fanny.

arbby · **Joined:** Thu Oct 18, 2012 6:22 pm **Posts:** 27

Thanks for the tips! It is new to me in September. I am in the Detroit/Windsor area. I obtained the 20 mpg on highway at 110km/h speedo/105km/hr GPS and Apx 1800 rpm. The brakes on the front and back were done in sept with the safety along with the parking brake. How do I check for the parking brake catching?

My father has a 2005 Libby crd and gets 10-11km/l stock. So I was hoping mine would be comparable.

I would like to get the GDE Eco tune but funds are tight for now.

I do try and get the best mpg by driving like a fanny at times too. :p

Thanks!

dirtmover · **Posted:** Thu Nov 15, 2012 9:22 am

arbby wrote:

I would like to get the GDE Eco tune but funds are tight for now.

Just one word of advice on the GDE tune. I procrastinated way too long on it and if I'd sprung for it back at the beginning of 2010 when I first started to view it as a serious option it would have paid for itself and I reckon I'd have about $200 extra in my pocket at the moment.

arbby · **Joined:** Thu Oct 18, 2012 6:22 pm **Posts:** 27

I may just need a Christmas present to myself!

Big Montana · **Posted:** Sat Nov 17, 2012 9:25 am

I'm on the Detroit side of the river (though north of Detroit thank God) and I have similar numbers this time of year. I have a short drive to work and home each day, and I never really warm up the engine. I drop to 21-23 MPG until March. Do check all of the above, because I've had all of these items go bad and they will each take 1-2 MPG off. On my best day with highway driving around 65 MPH, I killed a whole tank at 31 MPG. Otherwise in the summer I get around 26-28.

If you just performed the EHM, you may still have a ton of soot in the intake. It may take time to get all of that out of there. I'm not sure if that affects MPG though. That may just be performance.

Try power service too. I "think" I get better tanks when I use it, and start plugging your Jeep in if you can. I think it helps for my short drives each day because I reach operating temps faster.

Caddis · **Posted:** Sat Nov 17, 2012 10:12 am

The mileage on these things seems to be really variable, maybe that's true of any vehicle as I've never followed my fuel efficiency this closely before. There is certainly a sweet spot at about 1800 rpm's, and if you're willing to drive around there and not worry about keeping up with traffic, the little beast does a good job.
My mileage is pretty similar to Big Montana's. I live 7 miles outside of a small town in northern MN and during my normal weekly driving routine I'm down to about 23 mpg from 25'ish a couple months ago, obviously were getting winter fuel now. However, on a couple of long road trips to and from the Dakotas this fall, setting the cruise about 62, I was getting in the low 30's, and that was pulling a small dog trailer (approx 1000lbs). Pretty darn reasonable I think.

kapalczynski · **Posted:** Thu Nov 29, 2012 5:23 am

Check your thermostat (check your radiator with a infrared thermometer or something similar) and see what your operating temp is. make sure it is high enough to not be running the viscous heater constantly dragging down your economy. Clean you map sensor if you haven't yet and check for boost leaks.

:2cents:

maxwellp · **Posted:** Thu Nov 29, 2012 8:15 am

I put the GDE Tune in - Do it - Runs so much nicer. MPG was 13-17 all the time city and Hwy. Now with tracking every tank it is 21 city - 31 Hwy 65-70 mph. The Tune will be FREE after 10000 miles at just a 5mpg gain. Or if I drove on the Hwy all the time it would be FREE after 3333 miles. :pepper:

dirtmover · **Posted:** Thu Nov 29, 2012 9:22 am

maxwellp wrote:

I put the GDE Tune in - Do it - Runs so much nicer. MPG was 13-17 all the time city and Hwy. Now with tracking every tank it is 21 city - 31 Hwy 65-70 mph.

Your original mpg is not typical and you clearly had something very wrong that the GDE tune has addressed making your gain and payback somewhat artificial. The fact the you notice that it "Runs so much nicer" adds credibility to this theory. OTOH, if you'd gone to the dealer to address the mpg issue they'd have probably thrown more than the cost of the tune at it in parts and labour, that's if they even acknowledged that there was an issue in the first place.

As far as I'm concerned the difference in driveability that GDE provides is really very, very subtle and by far my main motivator for the tune is the mpg gain and getting rid of that darned CEL from the broken FCV that will result in an emissions fail.

Big Montana · **Posted:** Thu Nov 29, 2012 5:55 pm

dirtmover wrote:

As far as I'm concerned the difference in driveability that GDE provides is really very, very subtle and by far my main motivator for the tune is the mpg gain and getting rid of that darned CEL from the broken FCV that will result in an emissions fail.

But you're oil is clean right? I also have less "lag" before I take off from a dead start.

maxwellp · **Posted:** Thu Nov 29, 2012 7:29 pm

dirtmover wrote:

Your original mpg is not typical and you clearly had something very wrong that the GDE tune has addressed making your gain and payback somewhat artificial.

Could have been? But no other parts were changed. It was kind of a slug and the GDE tune made it more snappy so I think that it may not get driven as hard. (wifes car) :pepper:

She was used to the power of my Cummins, quite a bit more power. :BANANA:

fastRob · **Posted:** Sun Dec 02, 2012 12:27 am

I just got 16.7mpg last tank towing about 4500lbs in Albuquerque, NM, in the MOUNTAINS.
61 mph @ 27500rpm have 130,000miles on it.
Could I complain? I suppose.
I should buy a Cummins diesel truck but until this CRD dies gonna run it until it does really die dead.

arbby · **Joined:** Thu Oct 18, 2012 6:22 pm **Posts:** 27

Just a update. With new synthetic oil I've gone up to 16mg and 19mpg. So it's working better. I'm not driving as much as I got layed off work so I'm trying to stay in as much as possible ect. I will be going on a good 5-6 hour drive in a few weeks and that will clear some crap out.

I need to get the $$ together and have GDE take a look at it and stay a few days near them.

My thermostat is at 192. The heat blows TOO hot (from friends and fiancé).

MAP is cleaned
MAF is unplugged

I will check boost for leaks...

I really would like to do a GDE tune, smaco hoses, glow plugs. But Christmas, no work. Gotta have priorities.

arbby · **Joined:** Thu Oct 18, 2012 6:22 pm **Posts:** 27

Just a update. With new synthetic oil I've gone up to 16mg and 19mpg. So it's working better. I'm not driving as much as I got layed off work so I'm trying to stay in as much as possible ect. I will be going on a good 5-6 hour drive in a few weeks and that will clear some crap out.

I need to get the $$ together and have GDE take a look at it and stay a few days near them.

My thermostat is at 192. The heat blows TOO hot (from friends and fiancé).

MAP is cleaned
MAF is unplugged

I will check boost for leaks...

I really would like to do a GDE tune, smaco hoses, glow plugs. But Christmas, no work. Gotta have priorities.

Bad milage...what could be wrong?

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