How much loss in MPG are people seeing going from 2Hi to 4 Fulltime? Just curious.

Mine is a CRD but I'd assume it would be the same percentage-wise with the 3.7s.

None, you cannot loose mpg by changing to full-time. Many people on here say you do, I dont believe it. All the parts are already turning, they are just doing something when you put it into full-time.

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LOST KJ'S
Where are you going???
Current Jeep: 2004 Jeep Liberty
-Atlantic Blue
-Air Ride Rear Suspension ; OME/Rustys Lift ; Powertrax Locker ; Moog Lower Ball-Joints ; 245/70/16 Yokohama Geolander A/T-S's on MOABS ; Flowmaster 50 SUV
Lost #007082
http://www.cardomain.com/id/jeepjeepster

i haven't found any difference... if so it's probably negligible.

i’ve experimented with both & found no difference… so i run mine full time 4wd. in an emergency i have 4wd already engaged… too late to engage once you are backwards thru a fence…

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04 KJ Limited 3.7L

To me (in theory) there is a small loss when running between 2WD and 4 full time. This drop might be small enough to not notice if you are not hard on the gas pedal. But if you always stomp the pedal down, there could be a 1MPG change. Let me explain my thoughts: We all know that the entire front end of the liberty turns when 2WD is engaged but non of the power is being applied to the front half of the Jeep. When we run in full-time mode a percentage of the power (not all) now has to make a 180 degree turn at the transfer case and then power the front wheels. This is where I believe there is a small drop in effeciency.

Let me show you why I think this:
Work = F*d*cos(theta)

F=Force
d=displacemnet
(theta)= angle between the force and displacement vector

In our case (the Liberty MPG)
F is the same for 2wd and 4wd
d is also the same
but the angle now changes between 2WD and 4WD. however, since the change is little there is only a slight effect on the final result.

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02 Liberty Limited
Silver Outside & Taupe Inside
Heated Seats, Sunroof & Infinity speakers
USA Spec I-Pod adaptor, Mopar Sub, Garmin GPS
Tow Package, Select-Trac
Rock Rails, Tow Hooks

theoretically there should be no loss of MPG running in 4wd. It's simply taking the power and instead of routing it to all to the rear wheels, it routes it 50/50 or close to that. When you see that 4wd vehicles get less MPG that 2wd, that means all the time, and it's because the added weight of a front diff, t-case, etc.

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2004 KJ Sport 4x4 - Maroon
235/70/16 Firestone Destination A/T
T-Case and Engine Skids
Husky Front Liners
Escort PASSPORT-X50 Radar hardwired HIGH
ALPINE 9857 w/ full iPod controls
Infinity BassLink I Sub

I believe it's 48/52 but who's counting

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-nate
LOST#NL068123 - 2005 Renegade 3.7L 4x4, Off-Road Package, Rock Rails, Skids, Command-Trac, Trac-Loc LSD, Light Bar, K&N Drop in Filter, AMSOIL LUBES, RRO's Diff Guard for 8.25", Frankenlift, & Goodyear MT/R's
Cardomain

I ran my CRD in full-time 4wd for about two tanks. Averaged about 17-18 mpg.

Now I'm running it in 2wd and I'm on the second tank. Averaging about 17-18 mpg.

No discernable difference to me! LOL.

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Yours Truly,

Special Agent

Gosh, whats wrong with your crd?

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LOST KJ'S
Where are you going???
Current Jeep: 2004 Jeep Liberty
-Atlantic Blue
-Air Ride Rear Suspension ; OME/Rustys Lift ; Powertrax Locker ; Moog Lower Ball-Joints ; 245/70/16 Yokohama Geolander A/T-S's on MOABS ; Flowmaster 50 SUV
Lost #007082
http://www.cardomain.com/id/jeepjeepster

Was thinking the same thing. On my CRD don't see much of a difference in mileage. Would attribute an increase in fuel consumption with slowing down for conditions and running the engine longer for the mileage. In fact I just refueled and checked mileage today. Last tank ran in full time 4wd in the rain (it's a Goodyear thing) about 30% of the time, averaged 25.4 mpg on the tank.

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2005 Liberty Sport CRD, Lt Khaki, sunroof

Thankful to now be an EX-CRD owner.

darn, good mileage! I'm not sure what's up with my CRD, except that I'm running B100 and I'm in a cool, hilly area (Seattle).

But I'm thinking it's more of the "need a tsb/reflash/egr valve" thing? I'm not a gearhead, so I dunno.

Also, my CRD has just over 1,100 miles on it. Very new, I was waiting to see if this mileage improved over time as the engine broke in. Some other people (different board) were reporting low mileage numbers when new, some also reported unusually low mileage on biodiesel, more mpg loss than you usually suffer with this fuel in other engine types...

I would love to see higher MPG, so I'm going to switch back to Diesel #2 next tank and see just how much the fuel is affecting my mileage. Since I'm only doing about 50% highway right now, I dunno what my mileage "should be". Seattle is hilly, again, I'm sure that dents your mileage somewhat as well.

I'm guess I have more questions than answers. I also have the "hard start" syndrome, so I really am leaning towards the "need a flash" or whatever other TSB stuff was required to fix that. But I've sorta been hoping an '06 wouldn't need them.

*shrug* Aside from poor gas mileage and hard starts, thing runs like a dream. I'm happy with it DESPITE these problems. No shudder issues, strange noises or anything else. (And oh yeah, if I get on the freeway and set the cruise, at 60mph, I get about 24mpg.)

Sorry for the thread-jack, btw.

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Yours Truly,

Special Agent

Don't procrastinate on the TSB's, there are serious issues with this piece of engineering. When you take that in for the reflash, don't let them catch you or admit to using more than B5. Burn as much out as possible and refill with dino before your dealer visit. DC can void your warranty for "misfueling" this beast.

You're going to see some hard starts on B100, flash point is much higher. I try to run B20 which burns much cleaner than dino but fires slower in 0 to 10 degree weather cold starts. I wish my B100 pump was closer, want to bump up the bio usage but no competition and getting stupid expensive. Called them the other day, they raised their price $1.00/gal, now $3.50/gal. Can fuel with B20 for the same price as dino and no mess from storage and splash mixing.

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2005 Liberty Sport CRD, Lt Khaki, sunroof

Thankful to now be an EX-CRD owner.

I thought it was exactly 50/50, which is why you get binding when making turns on dry pavement.[/quote]

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2002 Jeep Liberty Renegade
3.7L V6 4x4, 5-speed manual
*Draw-tite class IV hitch
*Mopar rock rails
*Clear turn signals
*Mopar mud flaps
*Husky cargo liner
*'Trial Rated' and 'Renegade' emblems
*Bazooka 200 watt subwoofer

[/quote]

In the full-time mode, it is 48/52 (front/rear) but those figures are variable, since there is a viscous coupling or some other whackajamodingy thing that keeps the driveline from binding.

In the part-time, it's locked at 50/50. Also, Selec-Trac has full and part time 4wd, command-trac only has part-timer. They've both got the 4-lo, too.

If that's incorrect, somebody fix me up on it! And yes, a call to the DC Global HQ confirmed that the official part name is "whackajamodingy".

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Yours Truly,

Special Agent

Yeah, first servicing will be soon, I'll tell them my woes and have them put all the TSBs in. And I use ONLY dino-diesel in my Liberty, how dare you insinuate otherwise?! LOL.

As I said, I still gotta run a tank of dino and see how much of a difference there is... But it had hard starts on that very first tank of b5, so there you go...

Mostly I'll run dino for gas mileage comparison, I'm sure I'll need six dozen flashes done either way! LOL.

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Yours Truly,

Special Agent

Mine rattles like hell on dino. I think Jeep puts B5 in them to get it through the test drive and sold. B20 is sooo smooth, quite, and virtually free of soot. Thought it was cute when mine was in for a t-case seals. Service advisior was commenting on how smooth and quite it ran. Asked if I used premium fuel and where I buy it. Just had to smile and walk away.

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2005 Liberty Sport CRD, Lt Khaki, sunroof

Thankful to now be an EX-CRD owner.

my KJ was a selec-trac V6...even in snow (we still get a little in MN) I ran it in 2wd unless the snow was deep, then I'd throw it in 4 part time...

My school of thought is that there is less wear and tear on the vehicle in 2wd. If the pavement is dry, I see no reason to use 4x4 full-time. I only used the full-time feature on the interstate/some highways when the road was spotty (mostly clear pavement with some snow here and there). The full time is a neat feature (especially on a frozen lake-axis turns).

Another thing is tire wear. All wheel drives (which is what full time is) go through tires faster then a two wheel drive. If a tire goes bad on an all wheel drive, you are supposed to replace them all (tires get smaller as they age, this creates confusion for the T-case and diffs).

And I hate all wheel drives...no burnouts...accelerated wear...fuel economy can suffer (I saw a 1 mpg loss on a 4 hour interstate trip). It's also useless off road.

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'02 KJ Sport V6 4x4
3/8" Clevis lift
Rusty's 2.5 lift
255/70/R16 Fleet Farm All Terrain (yes they work)
Class 3 hitch
Hellas
Police Scanner/CB radio
LOST #: JH061986

http://news.yahoo.com/s/kcra/20060508/l ... wNtZW5ld3M

Not trying to steal the thread, but you guys were talking about gas mileage and the CRD...this link mentions a little something about that and other cars for that matter.

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06 White KJ Sport 4x4
http://www.cardomain.com/ride/2432458/1

Yeah, we've seen that. CR says 11mpg but that test has been shown to be wrong. They didn't take in to account that the diesel engine returns fuel to the fuel tank. So you can't just hook up an external tank and wait for it to run out of diesel. Half the fuel in that external tank went back to the Liberty fuel tank. They didn't hook the return line back to their external tank. Plenty of people have contacted CR about the correction but they won't do it.

I don't think an external tank was used for testing. The article says that a track was used and real world conditions. It might be mentoined elsewhere but this is the only reading I have done on the subject.

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06 White KJ Sport 4x4
http://www.cardomain.com/ride/2432458/1

I can't find the thread at the moment - but someone complained and CR explained their procedure and it used a seperate tank (they don't mention it in their publications)
No one else in the CRD group has ever gotten close to 11 - a couple have managed to get 16 mpg - generally towing something.

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2005 CRD
stuff
Skeptic quod gratis asseritur, gratis negatur