We drove from here in mid Florida to Moab via the I-40 route trying to maintain 65-69 mph (gps) and mpg ranged from 15 into a stiff wind to 20 or 21. Even in the mountainess areas like Highway550 in Western Co. the economy was good and this is an auto with 4.10 gears. If some of the fillups were free of alcohol that would account for the good numbers since alcohol does in fact diminish economy. Here is the lifted rig and it has a hardtop

 

Maybe we started from different tires. I had the 29" SRAs and have 4.10 gears.
I got over 20 mpg consistently on a 6000 mile trip when my JK was near new two
years ago. This past summer, on a 3000 mile trip, I got 16.5 mpg with the same
gears and 33" tires. These are calculated with a properly calibrated
speedometer/odometer. Tires make a huge difference; don't kid yourself.

By the way--probably no surprise here--but buying gas without alcohol seems to
give about 1 mpg more.

 

Not sure about the "lifetime" part (nobody can be until 2013 when the 1st 5-year inspections start), but I know in my case regearing helped my warranty case. My transmission burned up, as many seem to do, and the dealer said with 35's at least he knew the gearing was changed to compensate and wasn't part of the problem.

As a side note, after I got the gears put in and the bigger tires on, I had the dealer do what he could to adjust the computer. He couldn't get very close (that's why I have the Hypertech), but it was in his records that the speedometer and transmission shift points were corrected. That seemed to help my case too.

 

I noticed a difference.. especailly with the 35 12.50

 

LOL, I bet you did, I am having a really hard time right now because I think it looks really cool the way it is so I have no clue at this time what I am going to do.


THanks
Jim

 

The Toyota dealer sells the Prius since you're worried about mileage.

 

Really now!!!

I am not worried about about 13 MPG locally but when I take my trip across the US (as said in original post) I am looking at driving close to 6000 miles in a 2 week period, so figure a 7 mpg loss with the Jeep built equates to over a 160 gallon difference.... That's about $450.00 that I could use towards my new tires, wheels and lift.

I guess you didn't buy a Jeep based on your extreme intelligence.

I just hate that "why didn't you buy a priius" catch phrase. It may be my deep rooted psycho problem with environmentalists ...

 

You really need to be looking at a steeper set of gears as what robs fuel mileage from the automatics is kick downs and unlocking the converter. 5.13s are probably the right fit and will give you room to grow into 35s.

I too really dislike the comments pertaining to the purchase of a JK wasn't made based on fuel economy. The guy pulling 53 foot trailers didn't buy his rig for fuel mileage either but it is still a concern.

I keep very close tabs on my gas mileage because it lets me know when my engine is running most efficiently. Neither the aero differences of a lift or the additional weight of larger tires are going to make more than a nominal difference in fuel mileage. Where the majority of difference comes from is the increase in tire diameter and pulling your Jeep out of the power band.

With gears and a programmer you should be able to get the majority of your lost fuel mileage back. It's not going to work miracles, but it will improve things and make your JK more enjoyable to drive.

 

Here are the things I've confirmed to sap my mileage, previously an easy 22+ on the road, with occasional 24/25 trips:

1. Going from POS Goodyear Wranglers to the more aggressive BFG MTs
2. Stubbifying the OEM bumper
3. 2.5 lift
4. KC Daylighters
5. OEM bumper to LōD bumper with KCs mounted high
6. Leaving Lange mirrors mounted with the doors/mirrors still on

My road mileage is now typically between 19 and 20. I was surprised at how much effect the KCs had when they moved up from bumper height to the light bar on the LōD bumper. It was probably the biggest mileage killer, followed by the lift. Coming back from Michigan a few weeks ago, I was able to visualize the airflow, since it was raining and I had a mud-stained hood. Both lights had completely dry spots trailing behind them on the hood. I would flip them over, but they are designed to drain water out the bottom. If/when I get a winch, I'll re-evaluate their placement.


Confirmed to improve mileage:

1. Turning off OD for rural/suburban driving < 55 MPH or rolling hills


E3 plugs showed promise for a tank or two, but never sustained any long-term gain.
I removed my Wade ventvisors after the RR broke inside the window channel. I think they had a negative MPG effect, but never confirmed over multiple tanks.
Keeping the driver's window open (no Lange mirrors, no ventvisors) showed an apparent MPG increase when I was making out-back experimental runs one night. This idea was impossible to confirm/deny over multiple tanks, however.

 

New bumper sticker I'm debating getting.


And I use my JK as my daily driver...before the lift and tires: 18 - 19 mpg
Now: 15 - 16 mpg