I actually gained 10% in fuel mileage after the re-gear

[89grand]

Of course my fuel mileage still sucks, and it's not a concern of mine, but for 3 tanks before the re-gear I decided to check it, and I was getting about 11.2-11.3 mpg with 3.07's. I've checked it about 3 times after the re-gear to 4.10 and I'm getting 12.5. I can't beat that, better performance and better mileage.

Now I kind of have a lead foot, so I don't take off slow, or drive slow on the highway, so it could be better, but that's not the point. It did improve while driving the same way.

 

[Jerry Bransford]

The same thing happened after my regear from 4.88 to 5.38, my mpg went up from <12 mpg to 14.6 on the highway. Lower rpms do not always equate to better mpg.

 

[Shwiftypickle]

I'm glad to hear this I'm about to go from 3.07 to 4.56

 

[jjvw]

Similar here. The low end mileage increased a good amount, though the really high numbers I used to get on longer highway trips decreased a bit. But the overall average went up after the regear.

 

[89grand]

Yeah my numbers are a mix of highway and city. I think it probably improved quite a bit in city driving, and maybe the same or worse on the highway, but the average is better, and it's way nicer to drive now.

 

[Vinman]

I bought an 03 Rubicon with auto tranny brand new and ran the stock tires, 33” KO’s, then 33” MT/R’s, then 35” KO’s then finally 35” MT/Rs. I regeared to 5.13’s shortly after the final set of tires and the results were the best fuel mileage of any tire size I ran with the stock 4.10’s. Even better than 100% stock.

 

[ranger101]

Same situation with me. Went from 3.73’s to 4.88’s, got almost 250mi before the light came on, or roughly 16mpg.

 

[eastbloc]

Hate to party poop your discovery, but that is possible a too low of % to tell anything.
Have you been filling up at the same gestation?

I am on 31" tires and regeared from 3.07 to 4.56 around the same time you did.
MPG went down to 13's. When i first got this Jeep, it was doing 17-19 easily.

In the past years something happened, and mileage went down to 12-15 mpg.
I replaced spark plugs, O2 sensors, changed clutch just in case it was slipping... There were improvements, but never back to where it was, and over time it was still hovering between 14-15 mpg range.

Then i started to notice a trend between gas stations, some have constantly gave me crap mpg.
One day i had a curious idea to try ethanol free gas, i did, mpg went back up to typical 17-19. That gave me even more confidence about crappy gas assumption.
There is also another factor, with Jeep and 2 previous cars i have always got bad mpg after filling up at Chevron. Don't know what that is, but they always advertise some amazing fuel cleaning additives and their price is always higher, so i assume that those fuel cleaning additives is what killing the mpg.

Ethanol free = good
Chevron = bad
Other gas stations = 50/50
Conclusion: either crappy gas that is diluted with water or some chemical shit, or new spark plugs are picky.

*New spark plugs are Autolite XP985, the ones Jerry recommends to everyone, in case anyone is curious.

Yesterday i filled up with ethanol free again, and after 250 miles i am looking at 16mpg on new gears.

 

[Shwiftypickle]

Yours will be different anyway due to 4.56s on 31s. That's a lot of gear and little tires. I think all of it has to do with gearing, tire size and most importantly, how you treat the skinny pedal.

 

[eastbloc]

Yours will be different anyway due to 4.56s on 31s. That's a lot of gear and little tires. I think all of it has to do with gearing, tire size and most importantly, how you treat the skinny pedal.

Point i was making is that gas quality seems to vary from gas station to gas station. So unless you are religiously filling up at the same place and take same routs over a prolonged period of time, the 10% up or down difference over 6 fill ups says nothing about the effect of regear.

I put 150 miles on my Jeep every day. Believe me, after doing same routs for the past 2 years, i had plenty of things to notice and to think about while driving.

 

[AndyG]

Of course my fuel mileage still sucks, and it's not a concern of mine, but for 3 tanks before the re-gear I decided to check it, and I was getting about 11.2-11.3 mpg with 3.07's. I've checked it about 3 times after the re-gear to 4.10 and I'm getting 12.5. I can't beat that, better performance and better mileage.

Now I kind of have a lead foot, so I don't take off slow, or drive slow on the highway, so it could be better, but that's not the point. It did improve while driving the same way.

I believe it , and bet you will enjoy driving it so much more.

Why has amazed me is how much less deeper into the pedal you have to be to get it moving , and I have enjoyed being able to contend with traffic better.

I don’t know how to make improper gearing work... never could .

I realize you can drive a gear lower , but it was just never fun for me .

I’m convinced re gearing is essential , as installing large tires is just gearing the other direction.

 

[89grand]

Well, I think three fill ups before and three after the re-gear with nearly identical numbers before and after tells me something. No one is being party pooper because it wasn't like I was planning on throwing a party because I can go 22.8 miles further per tank now. Basically, the gist is that I lost nothing while gaining obvious power and driveability.

 

[DrDmoney]

The same thing happened after my regear from 4.88 to 5.38, my mpg went up from <12 mpg to 14.6 on the highway. Lower rpms do not always equate to better mpg.

I also get mid to low 14 mpg on 5.38’s with 35’s none of it is highway driving.

 

[Goatman]

Lugging an engine is worse that revving an engine. On normal road driving I'm never above 5th gear. Only when you are above 3000 rpm constant do I upshift. That 6th gear is way too deep of an overdrive for anything under 60 mph. But I bet a whole lot of folks are driving along in 6th gear thinking how great they are only showing 2000 rpm on the tach.

 

[Grant Lasson]

Then i started to notice a trend between gas stations, some have constantly gave me crap mpg.
One day i had a curious idea to try ethanol free gas, i did, mpg went back up to typical 17-19. That gave me even more confidence about crappy gas assumption.
There is also another factor, with Jeep and 2 previous cars i have always got bad mpg after filling up at Chevron. Don't know what that is, but they always advertise some amazing fuel cleaning additives and their price is always higher, so i assume that those fuel cleaning additives is what killing the mpg.

Ethanol free = good
Chevron = bad
Other gas stations = 50/50
Conclusion: either crappy gas that is diluted with water or some chemical shit, or new spark plugs are picky.

May I suggest looking into this a little deeper. In my area, most gas comes from the same refinery. "Brands" are more marketing than anything. Some brands mix-in some additives. The researchers when I was with Amoco who studied oils and gas were pretty clear that the additives didn't do anything good or bad.

That doesn't mean that any given gas station doesn't have dirty or watery tanks. It does suggest that there just isn't much difference in gas with a given octane or ethanol content.