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-   -   Better fuel economy..? (http://www.jeepgarage.org/f108/better-fuel-economy-44783.html)

JeremyJamesDec15 07-16-2012 08:52 AM

Better fuel economy..?
 
So I wanted some feedback from a few of you about feul economy. I have a 2012 WK2 overland summit 5.7. If I turn the knob to sport vs auto will I get better gas milage? Sport mode is suppose to transfer up 80% of the power to the rear axle, would this help with fuel econmoy over using the auto selection?

JRNYC 07-16-2012 09:03 AM

Re: Better fuel economy..?
 
I know it suppose to give better gas mileage around town due to the increase in shift points giving less "bog" in city driving.

Not sure about the 2 axle theory although it does make sense from my seat.

JeremyJamesDec15 07-16-2012 09:22 AM

Re: Better fuel economy..?
 
well the manual said sport mode transfers up to 80% of the power to the rear axle.

77rednecktruck 07-16-2012 02:03 PM

Re: Better fuel economy..?
 
I notice no difference in gas mileage in any of the modes. Tow/Haul feels the best but decreases gas mileage once the speed gets over 40 MPH since MDS is deactivated.

Yadkin 07-16-2012 02:58 PM

Re: Better fuel economy..?
 
In theory because you have less power going to the front axle you should get better economy. Add in the 1/2" lowering of the vehicle for decreased drag and you're probably taking about less than 1% increase- not something that you can reliably measure.

ColdCase 07-16-2012 04:32 PM

Re: Better fuel economy..?
 
I've seen posts here that those using sport for stop and go stop light to stop light type driving (where you are spending a lot of time accelerating), and then using auto for free flowing traffic (keeping it in eco mode as much as possible) get a little better fuel mileage overall, certainly less than 1mpg. Using one or the other exclusively won't provide the best fuel economy.

The sport shift points are better for starting from a stop or near stop, where the engine eco mode timing and valve adjustments and normal mode shift points are better for steady state driving.

Most here don't notice a difference. I use the mode that gives me the most driving satisfaction, it is a V8 after all, which is typically sport mode with MDS cruising, without MDS otherwise (5th).

ColdCase 07-16-2012 04:41 PM

Re: Better fuel economy..?
 
Oh, the power transfer % does nothing as the front axle and driveshafts are turning and adding drag to the vehicle regardless. You can put 100% on the rear (think the old select tracs with 2wd mode) and the front axle will still have a significant load. Those 4WD drivers that want max mpg look for front hubs that can be disconnected, which eliminated the spinning load of the front axles and drive shaft.

Now if you are constantly driving in a circle, there would be some load placed on the drive train by the transfer case clutches, but, I think, insignificant compared to the extra spinning mass. If the transfer case is locked there may be additional turning loss that could effect mpg.

jerkylips 07-16-2012 04:58 PM

Re: Better fuel economy..?
 
looked around a bit, didn't see one specific thread on this, but what kind of mileage is everyone getting with the hemi? I drive probably 75% highway / 25% city. I was recently given the green light to get a GC by the wife (she's as frustrated with the issues I'm having with the Liberty as I am).

I had/have myself convinced that the CRD is the right vehicle for me. That would still be my first choice, but I'm wondering what kind of a deal I might get on a 2013 once the 2014s are out. The CRD obviously is going to get significantly better mileage, but for the right price, the hemi could persuade me. Any thoughts?

ColdCase 07-16-2012 05:54 PM

Re: Better fuel economy..?
 
It depends on driving style and outdoor temperature. Those with a lot of city seem to get 15-16, those with a lot of highway get 20-21... but there are a few exceptions. I've seen as high as 23 on a long steady speed trip and a low of 16 in mid winter and plenty of city driving. I typically average 18-19.

JeremyJamesDec15 07-16-2012 06:00 PM

Re: Better fuel economy..?
 
My evic states I am getting an average of 14.1 MPG. I dont know how accurate the EVIC is though..?

Yadkin 07-16-2012 07:40 PM

Re: Better fuel economy..?
 
Its accurate when you are doing the same type of driving since you reset. But it has a funny algorithm that weights the more recent mileage to the display. So if you do 500 miles of highway then a few miles of stop-n-go it will show you have a low average.

jerkylips 07-16-2012 08:59 PM

Wow, that's better than I expected. I get around 16 with my liberty w/the 3.7. It's crazy how bad the mileage is..


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