radamsgfd

If you leave the stock wheels and tires on it can it be regeared to let the rpm's drop back to get better gas mileage? If so what gear should be ran? It will be ran on the highway as much as it will be in the city. I'm planning to leave it stock for now but i'm just not real happy with the gas mileage it gets, and would like to better it as much as I can. I've had lifted trucks before and regeared them to get back power i lost but I also noticed that my rpm's dropped back enough that I got better gas mileage also.

JPop

Best to get your rpms up to around 2300 or better at your prevalent highway cruise speed.

radamsgfd

I know that my other truck would tach 3100 at 70 mph with 3:53 gears and when we changed it to 4:11 it dropped back to 1900 at 70 mph which was a huge difference in my gas mileage. it would just sip fuel going down the road. I'm just not impressed with the gas mileage on the JK because I'm going from a V-8 to a V-6 and I was getting better gas mileage out of the V-8. Theres got to be something I can do to get better gas mileage out of the JK than 15 city and 19 hwy. I was getting 23 hwy out of the V-8. Is there anything I can do to get about 25 mpg out of the JK?

JPop

The aero drag on a JK is nearly certain to be bigger than your full size truck was. It's definitely a barn on wheels and hard to do much about things for efficiency.

Also, on the example you cited on your truck, you are dropping into an overdrive gear. I'm sure the V8 has ample power even at low rpms to keep your vehicle rolling. Unfortunately, the JK just doesn't have much if any power in reserve and you need to keep the rpms up to promote efficiency. Flat highways without overpasses, no wind and close to sea level you might be able to get away with 1800 rpms at highway speeds. That's probably not close to anyone's reality, and why I would look to be near 2300 rpm.

Other things you can do to promote efficiency would be replacing the stock can, aftermarket performance air filter and a programmer. That should buy you a couple mpgs but it's not going to get you close to 25 on the highway.

IcyFridge

I got 22 to 23 mpg on my 6 speed 3.21 when it was stock. Just play with the shifter a bit to get it at or around 2,300 rpm. I now have 33s on same gears and get 20 to 21 highway (with superchips).

CherryRedJK

I have done a lot of cruising around town the last few days with the top and doors off and I was getting 19.5 mpg without really trying. I never went to 5th or 6th gear and stayed around 35 to 45 mph. I found that a little odd that I was getting better gas milage in town than on the highway which is 17.5 if I'm trying, 16.2 with the doors and top off. And you dont buy a Jeep for the milage thats the price for an awesome ride.

Battlefrog

Shit, the only time I see 16+ is if I'm on the highway for a while... Usually, my mpg stays around 15.2-15.5... I've come to the conclusion that it is what it is, Which is a huge improvement from my 1500 ram even with the mult displacement hemi.. I was averaging 11.8-12.2 and getting 19 if it was a trip consisting of 150K + .....

IcyFridge

This was at 60 to 65. I will be taking a trip to my parents' house an hour away this Thursday. I will be running 70 to 72 most of the way.

Will keep you guys updated as always.

Krynn

I've seen close to the same with my stock '08 2 door 6 speed with 3.21 gears (anyone got any gears I can have?). I ran 4 hours down I-10 at 70mph according to the GPS and calculated 23.8 MPG for the trip.

On the other hand, that's along the gulf coast, where the only place the elevation changes more than 20 feet is on a bridge. I took a trip to Kentucky a few months ago, and once I got out of the flatlands I was only getting about 20 MPG.

I fully expect that when I put on 33s and regear, I'll see a drop to a max of 18~19. Lower if I go with 35s.

Here's some food for thought... From what I hear, the supercharged guys get 2~4 mpg better than stock. If they can resist romping on the gas, that is. That shouldn't be a problem when cruising down the highway though. Of course, I'd mostly likely burn much more around town putting that boost to good use!

JKlad

Yeah, I've found a huge difference in mileage between travelling at 55-60MPH & doing 70MPH & over.

In my stock 2-door 6 speed with 3.21s & 32" A/T tyres I get about 18-20MPG city & 25-26MPG higway at 55-60MPH (if the road's reasonably flat), but as soon as I notch it up to 70-75MPH & throw in a few hills it falls back down to 20-22MPG. There's a long, flat stretch of motorway in my daily commute with a limit of 50MPH & when I sit at that speed in 6th with the motor just turning over I can get around the 28MPG mark, so from my experience 55MPH seems to be the speed where wind resistance really kicks in on the JK with it's brick shape, near-vertical windshield, big fender flares and all the other un-aerodynamic stuff hanging off it (and that's a stock 2-door, let alone a modded 4-door with big tyres, steel bumpers & winches, armor & all the other stuff weighing it down & causing drag at the same time).