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  #1  
Old 11-15-2011, 07:23 AM
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Hemi Gas Mileage

I have a question for other members that own the new Hemi with the "fuel saving technology". I am under the impression that when I see the "ECO" indicator on my EVIC, it's telling me that 4 cylinders have cut out on the engine and I will see an increase in my gas mileage (why doesn't it do that when idling at a red light?).

I've been on long trips where 90% of my driving was on an interstate, using cruise control, and saw that "ECO" indicator for the vast majority of the trip, but yet I am not seeing much better than 20 or 21 miles a gallon average. To me, it seems that if I am going down to only 4 cylinders for the overwhelming majority of the trip, I should be getting much better than that.

I talked to my dealership about it and was told it takes a while for the computer to "learn" my driving style and as I put more miles on the car, the mileage will get better. I am over 5K miles now and still can't break 21mpg on a long highway trip.

Anyone else have similar experiences? Am I just expecting too much from a V8? I was not expecting 30MPG, but I was thinking that using only 4 cylinders would get me better than 20...
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Old 11-15-2011, 08:34 AM
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Re: Hemi Gas Mileage

Well, since the 2011 4x4 Hemi is EPA rated at 13 MPG City/19 MPG Highway and the 2012 at 13 MPG City/20 MPG Highway, I think that your highway mileage is pretty much what you should expect. Remember, your "four cylinder engine" is still moving a not so aerodynamic 2-1/2 ton vehicle! I've experienced similar highway mileage in my 2012 and am, quite frankly, very pleased with it, especially since I don't feel any performance compromise from the operation of the Fuel Saver Technology. Other than the ECO light on the EVIC, I don't notice it at all.

On the other hand, my city driving mileage on my local hilly roads has been as low as an abysmal 11.5 MPG.

When driving down a grade with my foot off of the accelerator and the transmission in "D" (i.e., drive), I've noticed more drivetrain resistance than I'd like. For this reason, I usually shift into "N" (i.e., neutral) when going down a grade that's steep enough to maintain my speed and long enough to make it worth the effort. Unlike the balky seven-speed transmission in my wife's 2012 Infiniti M37x AWD, the Jeep's six speed handles the shift out of and back into gear very smoothly. I typically don't engine brake, because the local hills that are steep enough to accelerate the Jeep significantly while coasting aren't long enough to make brake fade or wear a concern for me.

BTW, isn't there a TSB for a reflash of the 2011 Hemi transmission that makes it operate like the 2012 (i.e., more like a six speed than a five speed)? If so, you should probably make sure that you have the updated programming.
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Old 11-15-2011, 09:26 AM
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Re: Hemi Gas Mileage

My 2011 gets around 22 on long trips. More towards 14 around town.
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Old 11-15-2011, 09:55 AM
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Re: Hemi Gas Mileage

Few things.

#1. Even tho it says 'Eco' it doesn't mean that MDS is active. All it means is that you are currently driving within the bounds of the best possible mileage for the situation.

#2. 20+ MPG on a Big Dumb v8 4x4 is insanely good mileage. I have seen 22+ on mine with a fully loaded jeep doing 100% highway. If you want to see higher, drive a couple hundred miles at 55mph. You'll be able to see 24-25mpg.

#3. What is killing you is most likely the 10% non highway. In city traffic the engine is a gas slut. MDS is not active unless the car is running at a steady pace. So all stop and go is done at full power. This will easily shed 1-2 mpg from your avg.

Overall, don't worry about MDS. It does what it needs to do -- and it does it really well. Without it, I would guess we'd see about 17-18mpg MAX from this engine package. But with it, I guess a Polar Bear somewhere is sweating a lil less.

And, if you ever wanna 'check' to see if your MDS is active while at highway speed, and see how well it is working. Pull up the MPG EVIC screen, and then push your gear thingy to the left till it says '5' (or '6') and watch the MPG's Drop. You'll also be able to hear a slight change in the exhaust note as MDS de-activates. when you are done, push it to say 'D' and MDS will reactivate.
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Old 11-15-2011, 01:48 PM
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Re: Hemi Gas Mileage

Thanks for all the great responses. It seems that my mileage is right in line with everyone else. I'll check on that TSB as well.
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Old 11-16-2011, 09:41 PM
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Re: Hemi Gas Mileage

Consider your mileage outstanding! I drive I-294 (Chicago metro) daily, average traffic speed is 85. I consistently get 16 mpg.
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Old 11-16-2011, 09:57 PM
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Re: Hemi Gas Mileage

Maybe after some mods....you'll get better mileage.
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Old 11-17-2011, 12:43 AM
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Re: Hemi Gas Mileage

Quote:
Originally Posted by lll2for3lll View Post
Maybe after some mods....you'll get better mileage.
Don't count on it.
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Old 11-17-2011, 01:23 AM
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Re: Hemi Gas Mileage

I get better mileage after the 93 octane tune.
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Old 11-17-2011, 02:13 AM
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Re: Hemi Gas Mileage

Best mileage you will get is with cruise control on.
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Old 11-17-2011, 08:06 AM
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Re: Hemi Gas Mileage

Quote:
Originally Posted by ogbred View Post
Don't count on it.
I got better mileage (2mpg) out of my 05 Magnum R/T with Super Chips.
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Old 11-19-2011, 03:05 PM
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Re: Hemi Gas Mileage

Quote:
Originally Posted by Celly View Post
#1. Even tho it says 'Eco' it doesn't mean that MDS is active. All it means is that you are currently driving within the bounds of the best possible mileage for the situation.
According to the jeep.com website, ECO does mean that the Fuel Saver Technology (aka MDS) is active:

Quote:
ECO - Fuel Saver Indicator Off
ECO-ON - Fuel Saver Indicator On
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