Improved MPG with steeper gears.

[FastGlass]

On my first tank post lift, but when I swapped the axles out, I got em loaded with 4.88's. Also, 37" bfg km2's. I know the tires aren't true to size, but after plugging it all into the ProCal, my fuel economy seems to have gone up! I'm getting more than 1 mpg better than where I was. It also seems a bit more effortless to "go"...easy to chirp the wheels too

 

[HAFICON]

Nice.. *L* well with 4.88 and 34.4" tires I average 13.9MPG and I want 37s. Pulling my trailer i am 10-11mpg

 

[FastGlass]

See, Haficon, now you have me thinking I need to redo the ProCal and double check the tire size(s). The 37" BFG KM2's actually average out on the Jeep, under weight and from top to ground at 35.7"...I inputed the closest 1/4" to 35.75. Also with 4.88's.
I reset my odometers MPG averaging feature, and after tooling around for about 50 miles (albeit, all under ~45mph...only front wheel drive right now), I'm getting 15.5! WITH the Gobi...

 

[DallasJKU]

I get 1.5-2 mpg less with 4.10 and no lift but same tire size as my '13 Sport.

 

[Comanche Scott]

Front wheel drive vehicles seem to get great fuel mileage...

Years ago I read an engineering study in one of the trade magazines, in regards to axle ratios. In it the author made a good argument that some ratios are more efficient than other ratios in a specific differential.
I've noticed this, and have had comments from people I've built axles for, in this regard. But was never quite sure if it wasn't a placebo effect, so never followed through with any kind of study. Harmonics are definitely affected, and in steady state cruising, can effect mileage.
So yeah, maybe (and I certainly hope it works out that) you are. :friday:

 

[FastGlass]

Hopefully Scott
I'm starting to think once the rear DS is in, and the jeep is being pushed instead of pulled, it's going to go down. Regardless, as of right now, without waiting to go though the tank of gas and doing the actual math, I'm betting I'll be right around what I was averaging after I installed the rack...~14.5-15.5 mpg avg. I certainly didn't get another Jeep to worry too much over fuel efficiency, but was a little suprised there...

 

[Jurfie]

Jeez, I can hear it now: "next gen Wrangler will be FWD..."

But being able to choose between FWD, RWD, and 4WD would be sweet.

 

[Comanche Scott]

Jeez, I can hear it now: "next gen Wrangler will be FWD..."

But being able to choose between FWD, RWD, and 4WD would be sweet.

Used to be able to do that when Jeep ran the Dana 300 transfer case with twin stick option.

 

[SoCal Tom]

Front wheel drive vehicles seem to get great fuel mileage...
:

Small cars tend to get great fuel mileage, and small cars tend to have FWD. FWD does not improve mileage. Look up the Oldsmobile Toronado, big car FWD, same mileage as other Big *** cars of the day.
Tom

As for the original topic, lower gearing can improve economy two ways. First, it allows the transmission to spend more time in OD on the highway. Also, in city driving, it helps with acceleration, since it takes less throttle to overcome being stopped. There is a point where the higher RPMs eat the fuel economy benefits, so its a very narrow window where you can see this. ( plus the lower gears make it more fun to drive, so we start wasting gas "chirping the tires"
Tom

 

[Comanche Scott]

Small cars tend to get great fuel mileage, and small cars tend to have FWD. FWD does not improve mileage. Look up the Oldsmobile Toronado, big car FWD, same mileage as other Big *** cars of the day.
Tom

That was a joke Tom, as per the big grin...

 

[SoCal Tom]

That was a joke Tom, as per the big grin...

I'm still working on my first cup of coffee...., until the caffiene kicks in I have no sense of humor....

 

[rubicon91]

I am about 1300 miles into my regear (4.56) and about 500 miles into my new tires (35x1250x15) and I will say my mpg went up. I am averaging around 15-16 in town. I love it now. No clue what highway mpg gets but when I get the gobi it will at least not be any worse than what i was getting before regear.

 

[FastGlass]

I am about 1300 miles into my regear (4.56) and about 500 miles into my new tires (35x1250x15) and I will say my mpg went up. I am averaging around 15-16 in town. I love it now. No clue what highway mpg gets but when I get the gobi it will at least not be any worse than what i was getting before regear.

This is pretty much where I'm at...went a tad steeper at 4.88, but with Gobi and 37's, I'm pretty happy if when all is said and done, I continue to get the pre lift 14.5-15 mpg avg...

 

[oscar the grouch]

i get 17mpg on 37x13.5s in my rubicon manual trans on the highway. stop and go it drops to 15.5 ish

 

[DEFENDERBEAM]

try checking your speedometer vs. your GPS to see if the procal did the correct speedo re-calibration.

The GPS doesn't typically lie on your actual speed, so the vehicle speedo should line up pretty close.