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  #1  
Old 07-10-2012, 06:46 AM
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MPGs are taking a dump

so with the hot temps i have been running the AC more than normal and ive noticed my MPG has dropped down in the 13/14mpg on the highway. im taking it easy on the skinny pedal and using cruise control more often, have the superchips set on the 87 tune.

i had the spark plugs done and all my fluids changed at 60k, im approaching 90k. egr was done around 75k (?). so im wondering if theres something im missing that should be replaced. im due for an oil change in 2k, i run synthetic and ill be doing a filter change and drain/fill on the tranny at 90k as well. ill be swapping a dry AFE filter on my intake soon too. any other suggestions?
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Old 07-10-2012, 08:00 AM
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Re: MPGs are taking a dump

Something is wrong, either the engine is not running properly or maybe you have a sticking brake caliper. Could be something simple like a bad PCV valve or leak / crack in a PCV hose, or could be the tuner you are running. It certainly has nothing to do with any fluids if you are getting just 14 mpg. Try going back to stock tune, as I'm getting 22 mpg with my 5.7 on the HWY with the AC on with 105 temps outside on stock tune.
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Old 07-10-2012, 01:02 PM
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Re: MPGs are taking a dump

something is definately wrong, you should be around 20 on the highway even with the ac on
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Old 07-10-2012, 01:02 PM
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Re: MPGs are taking a dump

remove the tune and try it that way
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Old 07-10-2012, 01:54 PM
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Re: MPGs are taking a dump

even with 32s? comp says 15mpg today lol

may change the PCV this weekend. as for the caliper sticking idea- i do have a squeaky front brake thats annoying the hell out of me- maybe theres some unnecessary contact there?

i drove home with the windows down and the moonroof open and was getting closer to 16... such a pain in the ass. lol
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Old 07-11-2012, 07:49 PM
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Re: MPGs are taking a dump

Some observations:

MPG's typically drop somewhat with summer-blend fuels. They also drop when air intake is hot.

Has been in the 90's here for last 2 weeks; my IAT runs 95-125F in the late afternoon, depending on speed and traffic. Mornings, it is about 65F. Overall, it is 8-15F above ambient.

I lose 2-3 mpg's when AC is on and there is traffic congestion in town; otherwise 1-1.5 mpg loss when on cruise control with AC operational.

Can't address effect of your tune on mpg's as mine is stock.
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Old 07-11-2012, 08:08 PM
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Re: MPGs are taking a dump

I've gained about 1.5 mpg recently due to taking the roof rails off, no A/C, and gave my tires a little more air. Temperatures finally got out of the high 90s and back to the 80s, so now its 2 windows down and the sunroof open
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Old 07-12-2012, 07:13 AM
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Re: MPGs are taking a dump

so i looked at my maintenance records and within the last 30k i have replaced: egr, pcv, spark plugs, both tranny filters, etc..

i changed my tune back to stock yesterday and disconnected my battery to reset my adaptives and such- comp is showing high 18s on the jeep right now, but i havent ran my AC since. im currently running 35psi in my 32s. so i will run it this way for awhile and see what happens.

in the next couple thousand miles i will be doing another oil change, replacing both tranny filters and doing a drain and fill on the tranny. also i will be swapping to a dry-flow AFE intake filter.

being as a i do all highway driving and was getting less than 15mpg all highway- really was a kick in the ass. hopefully i can solve this before i bump to 33s. yes i know that will drop my MPGs but id like to get my mpgs up and as high as possible before that..
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Old 07-12-2012, 10:30 AM
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Re: MPGs are taking a dump

Quote:
Originally Posted by Blackout View Post
I've gained about 1.5 mpg recently due to taking the roof rails off, no A/C, and gave my tires a little more air. Temperatures finally got out of the high 90s and back to the 80s, so now its 2 windows down and the sunroof open
At over 50 mph, tests have shown better mpg is achieved by having your AC on than having the windows down, due to the aerodynamic drag. I've tested it on my WK and confirmed this.
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Old 07-12-2012, 02:05 PM
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Re: MPGs are taking a dump

I've seen drops in my MPG as well but thats bc i went from getting 19.5mpg in my V8 4.7L stock and then about a month ago, I put a 2" lift, bigger tires(265/70)and since its summer, my kayak racks are up.. im at 15 now and slowly climbing, I will probably settle at 16...

I assume having the jeep lifted, bigger wheels, kayak roof rack, and the warmer temps.. going from 19-16 is normal.

getting 14 is pretty low though. any other mods that will add the weight to it?
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Old 07-12-2012, 03:13 PM
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Re: MPGs are taking a dump

i have the factory front skid, and thats about it. lol...

im going to run it on stock tune for awhile, till i figure it out. maybe try the 91 tune for my trip to the beach at the end of next month.
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Old 07-12-2012, 04:19 PM
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Re: MPGs are taking a dump

Quote:
Originally Posted by dmsfun View Post
At over 50 mph, tests have shown better mpg is achieved by having your AC on than having the windows down, due to the aerodynamic drag. I've tested it on my WK and confirmed this.
Ya I know. I always use A/C on the highways.
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