MPG, when on 4WD

We've all felt the wrath of recent gas prices. So my question to you all is, does anyone else notice any significant increase in MPG when set to 2WD instead of auto or lock? I have not taken the time my self or driven enough to come up with conclusive numbers, so I was wondering if anyone else has any input on this.
 
So far the only way my MPG seems to be affected is depending on driving behavior, the more spirited driving leads to poor MPG ( obvious) and so on, but not sure if setting it on 4WD will have that much of an effect on it, we all know the manual says 2WD = better fuel economy, but I just dont see it.
 
your input is greatly apreciated, thanks.
Oto

When the dealer loaned me a 4WD, I played around with the settings and didn't notice much difference..but it wasn't exactly scientific..
 
Driving behavior will be a much bigger factor..
 
I get ticked at the people that race from lights and then slam on their brakes to stop...they're not getting there any faster than I am by averaging out my speed and I guarantee I'm getting much better mileage.
 
Everyone should read into hypermiling..just to get a few good tips..however they do go a bit overboard with some techniques that border on unsafe..such as driving 10 under the speed limit and tailgating semis

LOL, yeah I know what you mean about the street light racers.

I will be taking a trip this weekend and thought it would be a good oportunity to test this out. On my way up I will be driving on 2WD, and on my way down on 4WD(auto). I will post results on sunday when I get back.

It's hard to compare when you're going different directions due to the wind direction.
 
If the terrain is similar over the whole route, go half way in 2WD, then the rest in AWD...or split it into quarters

Good suggestion, I will do that.
thanks

you will get NO improvement in milage if you place the car in 2wd vs. AWD.
the componants are all still in complete motion (the axles and differential from the tires, and the propshaft from the transmission/transfer case).   The only difference is that the electro/hydraulic clutch that transfers power from the propshaft to the differential is not engaged.
Im not even sure why mitsu installed a 2WD mode, as its of no benefit in anyway.

Yes but although it's all in motion when power from the propshaft to the differential is engaged isn't there an increased load on the engine and less when disengaged?

From my 07 Outlander XLS 4wd...
I notice about a 1 MPG difference when the 4wd Auto is engaged.
Maybe from a 23 down to a 22 mpg average...Also possibly a greater loss in city traffic.
 
Please remember...this wasn't a scientific test.

1 MPG difference matches my observations also.

Also noticed that...
My 4wd XLS in 2wd gets it's best mpg at
55 mph/about 1600-1700 rpm/26-28 mpg.
 
Declines from there...
60 mph/about 1700-1850 rpm/23-25 mpg.
(No mods yet, just 5-20 synthetic oil.)

quote:

ORIGINAL: zontarh

Yes but although it's all in motion when power from the propshaft to the differential is engaged isn't there an increased load on the engine and less when disengaged?

shouldnt make any difference whatsoever, as its taking the exact same amount of force to turn all the componants.

I have returned from my small trip and will post my observations as soon as I get into work, to sum it all up, there is a bit of fuel economy to be expected from 2WD setting, but not considerably enough in my opinion.

quote:

ORIGINAL: Manybrews

shouldnt make any difference whatsoever, as its taking the exact same amount of force to turn all the componants.

 
That doesn't make sense to me, surely they can't just design a feature which disengages itself and claim it it improves fuel economy without evidence, they must at least have test results which back up their claims, and surely the engineers behind it wouldn't have designed it with the knowledge already of everything still moving would make no difference!

I think many brews thinks that just because the prop shaft and the rear axles are still spinning when the clutch is disengaged(2WD) that since everything is spining the engine is working just as hard as if the clutch was engaged(4WD), and that my friend is wrong. When you engage into 4WD your transfering some power to the rear wheels while still maintaining power on the front, and esentially making the engine work harder. just because when set on 2WD all the 4WD components are spining doesnt mean they are putting a load on the engine, the only load put on the engine is that of the weight of the prop shaft, the rear axle spins freely as the car moves forward as in any car. From what I noticed in my trip the MPG droped notisable in the stop and go of the city, probably about 1mpg wich matches whats advertised. But when I hit the highway, there was a varry minute drop of probably less than half mile per gallon, barely notisable. So I decided I will drive in 2WD on the city unless weather conditions force me to use 4WD, Although driving on 2WD inst that much economical than 4, I will drive in it for the most part, that 1/2-1 mile per gallon will account for some fuel savings in the long run.   

quote:

ORIGINAL: OTO27

I think many brews thinks that just because the prop shaft and the rear axles are still spinning when the clutch is disengaged(2WD) that since everything is spining the engine is working just as hard as if the clutch was engaged(4WD), and that my friend is wrong. When you engage into 4WD your transfering some power to the rear wheels while still maintaining power on the front, and esentially making the engine work harder. just because when set on 2WD all the 4WD components are spining doesnt mean they are putting a load on the engine, the only load put on the engine is that of the weight of the prop shaft, the rear axle spins freely as the car moves forward as in any car. From what I noticed in my trip the MPG droped notisable in the stop and go of the city, probably about 1mpg wich matches whats advertised. But when I hit the highway, there was a varry minute drop of probably less than half mile per gallon, barely notisable. So I decided I will drive in 2WD on the city unless weather conditions force me to use 4WD, Although driving on 2WD inst that much economical than 4, I will drive in it for the most part, that 1/2-1 mile per gallon will account for some fuel savings in the long run.   

let me explain how this system works..
transferring SOME of the power to the rears has absolutly no effect on the system.  Wether or not 100 percent goes through the front, or 50/50 goes to front/rear, it makes no difference on the drag on the driveline as ALL the componants are spinning regardless of 4WD setting.  There is no "extra" drag on the system when you engage the electromagnetic clutch on the rear differential.   The axles, rear diff, and propshaft all suffer the exact same amount of drag whether or not they transfer power.
The load on the engine is exactly the same, assuming you're not spinning the tires.  
the one and ONLY place this could make a difference it if you made many, many small u-turns or sharp turns, as some energy will be wasted in rear clutch slip.
thats it.
keep in mind that the propshaft is spinning due to the fact that the transfer case and transmission are always spinning it, not the road.  So that load hasnt changed at all.
the car also needs to expend the same amount of energy to spin the rear differential and axles in 2WD, as you need the engine to overcome the added drag of those componants.

you all can test till you're blue in the face, but if you keep testing over and over you'll find that the milage will be within 1-2 percent regardless of 4WD setting (which is well within a normal operational window, as milage will easily change that much due to a thousand different conditions).

truth is, the ONLY reason the "2WD" option is on there is because consumers requested it.   The 4WD system on this truck is identical to dozens of other cars/trucks on the road, and nearly no one offers a "2WD" option, because its just plain silly.

I understand now what you mean behind the theory of operation of the system, but how do you explain the increase in MPG that I observed while on 2wd, note that I did both calculations while going up wind and on a verry steady road, minimal bumps and it was at night with verry consistent temperatures, so the only variable was the car it self. Note also that the gain was verry small, probably less than 1 MPG, but gains none the less and would add up over time. If your theory is correct we should all write a law suite over to mitsu for false advertising " set the dial to 2wd for economical driving".lol. 

1 MPG is well within an allowed difference.. You could have easily been cooler outside one day, or less humid, etc.etc.

I dont believe Ive personally seen any advertisment stating that you will get better milage in 2WD, but I admit to the fact that I havent done a lot of research on all the marketing.
The only possible difference between 2 and 4WD is that in 4WD you will have a heavier electical load (to activate the rear clutch), thereby causing a slight amount of added drag on the engine via the charging system.. But thats really grasping.

quote:

ORIGINAL: Manybrews

1 MPG is well within an allowed difference.. You could have easily been cooler outside one day, or less humid, etc.etc.

I dont believe Ive personally seen any advertisment stating that you will get better milage in 2WD, but I admit to the fact that I havent done a lot of research on all the marketing.
The only possible difference between 2 and 4WD is that in 4WD you will have a heavier electical load (to activate the rear clutch), thereby causing a slight amount of added drag on the engine via the charging system.. But thats really grasping.

 
I can't say I've read it in any satement by Mitsu either, it's mostly showing up in reviews but
my dealer stated 2WD for greater fuel economy when explaining the controls at hand-over of the vehicle, he must have been briefed by somebody at Mitsubishi!

However or wherever it's engaged, there's going to be some driveline friction between the point of disengagement to the hub

lol, interesting discussion to read!! I think Manybrews has a good point with his theory, but doesn't the load on the rear differential when engaged in 4WD have an impact on the rest of the driveline?
I think Manybrews will agree that the slightly better fuel efficiency in 2WD doesn't really justify the additional cost of designing and implementing an intelligent 4WD system in an SUV... I think it doesn't really add much value in comparision with a hybrid car setup. Of course the latter costs much more money to develop, but on the long term... the only way to get MPG down

I have to admit manybrews made the light bulb on top of my head come on, and I do understand what he is saying now, but I still dont think the only reason they would put that 2WD function there is just because of customer request, there has to be something we dont know or are not getting behind the system. After all the manual does state "2WD= better fuel economy" and it really offers that to a certain extenct, in the city at least.

quote:

ORIGINAL: OTO27

I have to admit manybrews made the light bulb on top of my head come on, and I do understand what he is saying now, but I still dont think the only reason they would put that 2WD function there is just because of customer request, there has to be something we dont know or are not getting behind the system. After all the manual does state "2WD= better fuel economy" and it really offers that to a certain extenct, in the city at least.

trust me, the main reason its there is because customers requested it.   For whatever reason, a lot of people have their heads in the sand over AWD, as though it would be beneficial to be able to shut it off.  Many people complained that the old Outie was either 2WD or AWD, with no choices.
Well, they implemented the choice just to make people happy, but its not the same as on an old pickup truck... On MOST 4WD trucks, the front axles, differential, and driveshaft do not spin unless in 4WD.  On this setup everything is spinning, but there is no torque transfer from the spinning propshaft to the pinion of the differential due to the electronic clutch that is placed between the two.   Even the clutch plates are spinning!   there just isnt any friction between them, similar to having your foot on a clutch pedal whilst the engine is running.

heres an example of a Haldex AWD coupler, which is nearly identical in operation to mitsus system.  The part in green is the clutching mechanism.  In 2WD on an outie, the clutch is totally disengaged, so you can see how no torque will be transferred.  But you will also see that in fact every componant is spinning at whatever road speed/transfer case speed is present.

I am no engineer, just a thinking average Joe, and the article on the 4WD system of the Outlander (found HERE) is more than enough for me to understand that 2WD offers the best fuel economy. People argue some of the features of this vehicle are gimmick (e.g. paddle shifters, 2WD mode, 4WD Lock which isn't truly a "locked" mode), well, to each his own I guess. But I still go by the words of the manufacturer, since they made the vehicle, they probably know more about it than anybody else.

Fuel economy between 2WD and 4WD Auto is a moot point to argue about. Unless maybe you work for the EPA and you have access to a lab that can truly scientifically measure the fuel consumption between the 2 modes under strict controlled environment. But running your car on the road and saying you got it figured out, hmmm, I doubt it. Although I would agree that the margin of fuel economy will be slim, and perhaps it would only become practical after 4 to 5 full tanks. So driving your Outlander in either modes, in a real world stop-and-go traffic, will not give you practical savings to prefer one mode over the other. But despite the impracticality of it, there being no "tangible" savings using either modes, it's never a point against a "gimmick" 2WD mode. The 2WD mode does it's job of being the best fuel economy mode (although by a hairline margin). The point of contention should be the great fuel economy the 4WD Auto has to offer. It's so efficient in giving you the right torque at the right conditions, and does that while maintaining a fuel economy close to driving in 2WD mode. Isn't it great you can actually drive in this mode and yet get mileage as if you're on 2WD?  And that's why I guess Mitsubishi labeled it as the "default" mode on this vehicle. What if there was a big gap in fuel economy between 2WD and 4WD Auto? You'd be forced then to use 2WD just to maintain your great mileage. Me, I'm just thankful I get to drive my Outlander in 4WD Auto mode and yet save on gas.

Hey "Manybrews"!
Do you own a '07 XLS 4WD? 
Or, are you just speaking your mind based on your own theories?
 
All the '07 XLS 4WD owners seem to agree with each other based on experience.
You seem to be getting kinda sensitive about the whole subject.
Just curious...Take care!