LOST JEEPS :: View topic - MPG Loss By Running 4Full?

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.

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.

Special Agent wrote:

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.

Gosh, whats wrong with your crd?

Jeepjeepster wrote:

Gosh, whats wrong with your crd?

Was thinking the same thing. ...averaged 25.4 mpg on the tank.

RFCRD wrote:

Jeepjeepster wrote:

Gosh, whats wrong with your crd?

Was thinking the same thing. ...averaged 25.4 mpg on the tank.

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.

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

Quote:

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

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

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.

RFCRD wrote:

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.

http://news.yahoo.com/s/kcra/20060508/lo_kcra/3452610;_ylt=As2LC0MMwC2a.BAr0XySCHUDW7oF;_ylu=X3oDMTBhZDhxNDFzBHNlYwNtZW5ld3M

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.

Sport wrote:

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.

Author:	NetJunkie [ Tue May 16, 2006 10:32 pm ]
Post subject:	MPG Loss By Running 4Full?
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.

Author:	Jeepjeepster [ Wed May 17, 2006 5:28 am ]
Post subject:
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.

Author:	sini [ Wed May 17, 2006 5:59 am ]
Post subject:
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…

Author:	sleeve84028 [ Wed May 17, 2006 11:03 am ]
Post subject:
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 = Fdcos(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.

Author:	nickmv [ Wed May 17, 2006 11:06 am ]
Post subject:
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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MPG Loss By Running 4Full? http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=1&t=8604	Page 1 of 2

Author:	Guyute1210 [ Wed May 17, 2006 11:52 am ]
Post subject:
nickmv wrote: 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. I believe it's 48/52 but who's counting

Author:	Special Agent [ Wed May 17, 2006 4:26 pm ]
Post subject:
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.

Author:	Jeepjeepster [ Wed May 17, 2006 5:41 pm ]
Post subject:
Special Agent wrote: 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. Gosh, whats wrong with your crd?

Author:	RFCRD [ Thu May 18, 2006 12:07 am ]
Post subject:
Jeepjeepster wrote: Special Agent wrote: 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. Gosh, whats wrong with your crd? 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.

Author:	Special Agent [ Thu May 18, 2006 2:28 am ]
Post subject:
RFCRD wrote: Jeepjeepster wrote: Gosh, whats wrong with your crd? Was thinking the same thing. ...averaged 25.4 mpg on the tank. 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.

Author:	RFCRD [ Thu May 18, 2006 6:36 am ]
Post subject:
Special Agent wrote: RFCRD wrote: Jeepjeepster wrote: Gosh, whats wrong with your crd? Was thinking the same thing. ...averaged 25.4 mpg on the tank. 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. 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.

Author:	ShoreRenegade [ Thu May 18, 2006 9:35 am ]
Post subject:
Quote: I believe it's 48/52 but who's counting I thought it was exactly 50/50, which is why you get binding when making turns on dry pavement.[/quote]

Author:	Special Agent [ Thu May 18, 2006 10:47 am ]
Post subject:
ShoreRenegade wrote: Quote: I believe it's 48/52 but who's counting I thought it was exactly 50/50, which is why you get binding when making turns on dry pavement. [/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".

Author:	RFCRD [ Thu May 18, 2006 11:53 pm ]
Post subject:
Special Agent wrote: RFCRD wrote: 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. 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. 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.

Author:	ManicMechanicJoe [ Sat May 20, 2006 9:28 am ]
Post subject:
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.

Author:	ATXKJ [ Wed May 24, 2006 2:22 pm ]
Post subject:
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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Author:	Sport [ Wed May 24, 2006 1:19 pm ]
Post subject:	Government gas secrets
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.

Author:	NetJunkie [ Wed May 24, 2006 1:22 pm ]
Post subject:	Re: Government gas secrets
Sport wrote: http://news.yahoo.com/s/kcra/20060508/lo_kcra/3452610;_ylt=As2LC0MMwC2a.BAr0XySCHUDW7oF;_ylu=X3oDMTBhZDhxNDFzBHNlYwNtZW5ld3M 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. 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.

Author:	Sport [ Wed May 24, 2006 1:28 pm ]
Post subject:	Re: Government gas secrets
NetJunkie wrote: Sport wrote: http://news.yahoo.com/s/kcra/20060508/lo_kcra/3452610;_ylt=As2LC0MMwC2a.BAr0XySCHUDW7oF;_ylu=X3oDMTBhZDhxNDFzBHNlYwNtZW5ld3M 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. 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.