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  #1  
Old 02-08-2014, 11:47 PM
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Angry My 2012 Summit V8 dropped mileage down to 10mpg?

I have a 2012 Summit with the V8 and averaged 12mpg since I did predominately city driving. Highway mileage was 18-20mpg.

Now I have 11k miles and the mileage has dropped to 10mpg. Is this bc of more ethanol in winter gas or should I try a different octane or is it my heavy foot? It seems like applying the slightest throttle now takes it out of Eco.

What could explain the mileage drop and should I bother taking it to the dealer?
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Old 02-09-2014, 12:01 AM
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Re: My 2012 Summit V8 dropped mileage down to 10mpg?

I would take it in. I know that it is a V8, but 10 MPG is just terrible, and 12 MPG isn't too great either. Either something is wrong or you are driving it flat out constantly.
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Old 02-09-2014, 05:59 AM
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Re: My 2012 Summit V8 dropped mileage down to 10mpg?

Q= Did you recently bring your Jeep to the dealer ? do you know if the Flashed your computer for a TSB ?
I was getting the same mileage as you were, I brought mine in for the 50000mi Trans fluid change and they said there was a TSB for the transmission after they did the Flash I went from 18-22 down to 10-13 I called them and let them know, They said give it time for the computer to Learn the new program installed, Ok I would agree with that thought. After 1500mi had them REflash it and YES No luck but I am still waiting for the computer to learn (3000mi after the 2nd flash) I am going in to have them install my Rock Rails next week they say 1.5hrs to install them so they should have Plenty of extra time to figure out why my MPGs dropped after the flash. I am just coming up on the 60000mi spark plug change and I am Sure they will go with that as an excuse
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Old 02-09-2014, 08:56 AM
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Quote:
Originally Posted by JMP8562 View Post
Q= Did you recently bring your Jeep to the dealer ? do you know if the Flashed your computer for a TSB ? I was getting the same mileage as you were, I brought mine in for the 50000mi Trans fluid change and they said there was a TSB for the transmission after they did the Flash I went from 18-22 down to 10-13 I called them and let them know, They said give it time for the computer to Learn the new program installed, Ok I would agree with that thought. After 1500mi had them REflash it and YES No luck but I am still waiting for the computer to learn (3000mi after the 2nd flash) I am going in to have them install my Rock Rails next week they say 1.5hrs to install them so they should have Plenty of extra time to figure out why my MPGs dropped after the flash. I am just coming up on the 60000mi spark plug change and I am Sure they will go with that as an excuse
Not sure if you saw my review or not, but tell your dealer good luck with the 1.5 hours. It took my dealer 12 hours, and they charged me $600.
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Old 02-09-2014, 10:29 AM
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Re: My 2012 Summit V8 dropped mileage down to 10mpg?

Yes I have read some write-ups on the rock rail installs and it would take me 1.5hrs to remove the plastic sill guards and I have prepaid the rails and labor, told them I will have a family member pick it up and I would like to get it paid in advance They were ok with that do I feel Guilty for doing that to them NOPE well a LiL...but I will be the one to pick it up 2 days later just to make sure they did a good job. and I will print a few pages from the forums to give the Poor guy that gets stuck doing it some helpful tips and tricks to get it done Properly.
anyone know a good write up that i can share with them ? I would appreciate the help but he/she would LOVE the help.
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Old 02-09-2014, 10:41 AM
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I've always done 12 in the city since day 1 with my 2011 Summit hemi. Just par for the course I think.
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Old 02-09-2014, 10:58 AM
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Re: My 2012 Summit V8 dropped mileage down to 10mpg?

I'm getting 10 mpg too. I drive it like a race car most of the time. I had the TSB flash for improved shifting done. 2012 with 5.7L V8. The gas in our area changed and it's 87 octane with 10% ethanol (and winter blend gas, whatever that is) and is 20 - 30 cents cheaper then before, so I'll live with this. I still seem to fill up about the same number of days though.
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Old 02-09-2014, 12:57 PM
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I have a 2014 SRT with 1800 miles and I am at 11.4 mpg . Just about all 1800 mile have come in the city. When on the highway in Eco Mode I seem to get around 20-24mpg but only have been on the highway a few times.

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Old 02-10-2014, 08:25 AM
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Re: My 2012 Summit V8 dropped mileage down to 10mpg?

... and yes, you'll see a mileage drop with the winter blend as well.
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Old 02-10-2014, 08:09 PM
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Re: My 2012 Summit V8 dropped mileage down to 10mpg?

Now I'm getting 12.1 mpg.
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Old 02-10-2014, 08:46 PM
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Since I just installed a hemifever tune in mine I started watching close. I babied it today and I'm over 12 with MDS disabled.
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Old 02-11-2014, 11:49 AM
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Re: My 2012 Summit V8 dropped mileage down to 10mpg?

In pure city driving -- stop-n-go, or small-town 25 MPH driving, I can easily see the Hemi only getting 10 MPG in winter. I always drop 1-2 MPG in the winter -- on all my vehicles. My Hemi Ram gets in the 12s in the winter, and that's a "mixed" commute of some highway. It's a 4x4 Crew with 3.92 gears, and heavy LT A/T tires in OE size. If I were doing small-town driving, I'd be lucky to get 10 mpg.
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