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2008 with the old 3.8 and 175K miles. We are on vacation in Northern Lower MI and I decided to lock it in at 65mph for the 250 mile drive (also pulling a small 300lb trailer)..

The Jeep is my DD and I get around 16.5-17mpg going 70mph (30 mile one way highway drive to work).

For this trip I calculated it to be 18.6mpg! I'll take it!

I know - not as good as you Pentastar guys... but not bad for a 3.8!
 

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Its good to go slower in the Jeep. Where did you vac? I love the TC/Suttons Bay area.
I have many Michigan ties with the main one being my wife. Sheeeess a Yooper!

BAck on track, my Jeep computer says I am getting 19.3 around town on 34.5's and a whole lot of extra weight in mods. It seems pretty accurate for the most part. Now I am planning on swapping the 3.21's for better 4.56's. Truthfully I would still drive it if I got 10 mpg.
 

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We are on Lake Huron between Cheboygan and Rogers City... Been coming up to my folks place since I was a kid in the 80's - now I have two of my own to bring!


I'm just running 33's and stock everything except front bumper.. so not extra weight to speak of.

Doing lots of research on "upgrading" my trailer with larger wheels and building something like an old Bantam style box.
 

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Love Northern MI. We're from down state around the Ionia area. Just spent the fourth at Clear Lake State Park south of Onaway. Prob almost drove right by you when we drove up to Mackinaw City for a day. Also, We too just love the Leelanau peninsula, as well as the UP. Niece is now going to Northern, in Marquette. Can you spell Road Trip??? LOL

Back on above track. I wish I could approach 18-19 mpg. I'm getting 15-16 with my 08 JKU 3.8 with Teraflex 2.5, same as above Duratracks (which we love), no other major mods yet.
 

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65 would be dangerous on Florida highways
 

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I was able to get to about 21.5 mpg on flat highways when driving from Austin to Dallas. Once I hit any type of hill, I'd be back to around 18-20 mpg. That was traveling at 63 mph in 6th gear with a 3.8 with 3.21s and cruise on. I also drive a jk 2dr with stock 17 inch stock MT tires.

The only issue is when I hit a hill for a long period, I have to downshift to 5th tovkeep a steady speed.
 

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"For this trip I calculated it to be 18.6mpg!"

My own 08JK likes that speed as well with 3.73 diffs.

The extra 5-8 mph to hit the 70+ area is pretty spendy in terms of mpg.
 

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08 3.8 208,000klm Auto 3.73. SuperChips programmer on Premium. 18-19mpg highway on 37" Pitbulls with Overdrive off (final ratio equivalent of 5.13) max speed I run is 65mpg, but usually around 55-60. At 60mph with OD off the engine runs 2100rpm, it's sweet spot.

Yes premium makes a difference but you need to have a programmer to tune for it. If you don't have a programmer for your 3.8, get one, you'll be amazed the difference it makes.
 

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65 would be dangerous on Florida highways
I understand this completely. I rented a car a couple years ago and drove along I-95 in the Melbourne area, they should just shut down the whole highway and give everyone a ticket for going 30 MPH over the limit. People call Californians crazy - shee yit.

I've experimented with various speeds in my JKUR and found 65 does very nicely on MPH, 20 - 20.5 That little bump to 70, knocks it down to 17.5-18

I'm driving a box down the road, how should I be surprised? :doh:
 

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I just went shopping. On the way to the outlet mall I drove my 2015 JKUR / 3.73 / 33" / AT at 60 mph.

Got 20.5 mpg per the computer.

On the way back drove 65

Got 18.7 mpg.
 

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^^^^ this !
My exact thoughts... :)

(or Momma bought so many pairs of shoes it weighed the jeep down :) !)
 

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Magic number before the economy drops off a cliff for our '12 JKUR is 70 mph. Under that and it just gets better. Go 55, and it will get over 20mpg all day. Of course that's not realistic in most areas.

Got this on a dirt road coming down some pass in CO, but regularly saw 21 mpg on that trip at just under 70mph.



Now what will totally kill economy is wind + speed. Heading one way for a trip with no wind I got 19+ at over 70. On the return and against the wind, it dropped to 17.

If I'm on flat ground towing the 3500 lb camper and no wind, I can get 17 pretty easy (now that is at the Kalifornistan limit of 55). However, put the silly roof rack on, add 2 100 lb mutts, mom, baby, the cheeseball roof rack and go 70 mph (sick kid who already yarked in the car and we wanted to get home) and a decent bit of wind and we got barely over 10 mpg!!!! That's almost as bad as we get on the Rubicon (9mpg).

 

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65 would be dangerous on Florida highways
LOL.... so true!

If I drove 200 miles at 65 on cruise control, I would fall asleep and kill myself and/or half a dozen other people. No thanks.... for me, 85 is more like it.....A longer life is worth a little extra gas.
 

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Before my tires, I did 65 -70 as traffic allowed, mostly cruise control, and was hovering around 21 on my 2d. That's from STL to KC, so some good hill action in there. Stayed right and just chilled out.
 

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Before my tires, I did 65 -70 as traffic allowed, mostly cruise control, and was hovering around 21 on my 2d. That's from STL to KC, so some good hill action in there. Stayed right and just chilled out.
St Louis to KC has some hills? :funny post:

Try going over Sonora Pass where there are 28 degree inclines with a 3500 lb camper.... :D
 
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