Age old question - MPG specific on 3.6 jku auto with 4.88 gears in 35s
09-05-2023, 09:13 AM
#1
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Age old question - MPG specific on 3.6 jku auto with 4.88 gears in 35s
Hello everyone,
Just looking to get some real numbers on mpg with the 3.6 auto on 35s with 4.88 gears. Looking through threads I have found some data but alot mixed with manual transmissions.
I am looking at buying this set up and mostly concerned with extended highway driving since I’m planning on long trips with speed limits around 75ish.
Just looking to get some real numbers on mpg with the 3.6 auto on 35s with 4.88 gears. Looking through threads I have found some data but alot mixed with manual transmissions.
I am looking at buying this set up and mostly concerned with extended highway driving since I’m planning on long trips with speed limits around 75ish.
09-06-2023, 09:04 AM
#2
JK Newbie
I have that setup and can't really speak to the mpg exactly, as I haven't hand calculated anything. I can tell you, that it isn't great. at those speeds, I'm around 3000 rpms.
09-06-2023, 12:36 PM
#3
Super Moderator
That is an interesting question and will be interesting to see any replies. FYI.. I run a 21 Mojave Gladiator with 4.10s and 8 speed auto on 35s and at 70+ mph on cruise I see low 16s.. drop down to 60 up into 17s-18s. I'm of the mind set that JK with the older auto trans & 4.88s is probably, at 75, going to be around the 15s-16s just my opin and will be turning much more RPMs.
09-07-2023, 08:22 AM
#4
Super Moderator
75mph and gas mileage are just a bunch of words that don't go together. And there is the big lack of aerodynamic efficiency to take into account. My V8 gives me 22mpg (us gal) at 70mph into a 10mph headwind. Thats because the engine does not work and my tires are smaller at 34" and 285 wide. Just to give you an idea what wind costs you and the wind force is equal to the square of the speed so doing 65 is way better than 75. I once owned a 1998 Dodge 2500 12V diesel manual. On the hiway empty I got 26mpg (imp) at 65mph. Pulling a flat deck trailer all up at 3 tonnes gave me about 24mpg. My 8ft camper that weighed just under a tonne gave me 14mpg every day. It was the pushing of the wind that killed the mileage. So the best way to get gas mileage is to slow down and enjoy the ride in the right lane. Thats what I did even in Texas with 80mph speed limits.
The following 2 users liked this post by Sixty4x4:
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09-07-2023, 10:20 AM
#5
JK Jedi
It ain't gonna be great, and it shouldn't matter that much. In that box, you'll notice a big difference in fuel economy heading down the interstate at 65, 70, 75, 80mph. If it got 14mpg vs. 15 or 16mpg, is that going to be a game-changer? I would bet you are around 15 mpg +/-. I get about 13.5mpg on average in my heavy jeep with 37s.....that should make you feel better.