Gas mileage with 4.56s/4.88s and 35s and 31s w/ 4.10s?

ZachMan · Apr 1, 2004

Got a 2000 XJ about to go under major surgery, just as gas prices keep going up and up.:bawl: Planning on 4.88s w/ 35s, but I might go 4.56s if it help my mileage. (I drive alot, especially hwy) Just wondering what to expect mpg wise so I won't pass out at the pump. If it matters stock I got 18 mpg mixed driving.

Also, my girlfriend is getting an RE 3.5" and 31s w/ 4.10s. Just wondering what she should expect mpg wise?

Thanks

Lincoln · Apr 2, 2004

If your going to 35's it isn't going to matter. If you go to 4.56's your smoking dope.

http://www.naxja.org/forum/showthread.php?t=13851

ZachMan · Apr 2, 2004

Lincoln said:
If your going to 35's it isn't going to matter. If you go to 4.56's your smoking dope.

http://www.naxja.org/forum/showthread.php?t=13851

Must be alot of dope smokers. Anyone who still runs their 8.25 w/ 35s is running 4.56s. Yeah I am probably not, but still with 200+ hwy miles alone each week, maybe.

Lincoln · Apr 2, 2004

Actually you will probably find most of them wishing for 4.88's.

Seriously, go to 4.88's. Lifting it up and increasing the weight your trying to turn is going to be taxing. The 4.88's will keep the motor from trying hard to maintain speed. I bet you would get less mpg with 4.56's than 4.88's because your foot will be burried more. 4.88's are the minimum I would ever try and run with 35's and that would depend mostly on the OD ratio. I've had 35's waiting to go on for about a year and I won't put them on until I have gears. 5.13's or 5.38's.

I think the 4.10's for 31's would be a wise choice if bigger tires weren't in the future. I ran my 32's with 4.10's (auto) and new it was a mistake less than a week after I got them, wishing for more gear. I've been told the OD in the standards aren't as high and that would have probably made it a little different.

I still think if your talking 35's gas mileage is a mute point.

ChuckD · Apr 2, 2004

If your running that many freeway miles why not just get a beater, that gets over 25 mph. Why put those miles on your XJ and on those expensive 35" tires.

Does this make sense?

ZachMan · Apr 2, 2004

Because I am saving for a beater 2005 Dodge Ram CTD 2500 QC 4X4. Plus I will have 35" Mud Kings that I got for $300 brand new.

You got to think whats the difference in mpg between 31s w/ 4.10s and 35s w/ 4.88s? Even if I just wanted a small lift and 31s its gonna be about the same, right?. I think I have seen people say to expect 15 mpg. average.

ZachMan · Apr 2, 2004

ChuckD said:
If your running that many freeway miles why not just get a beater, that gets over 25 mph.

That doesn't make sense, if I can't go 70 mph I can't go...

Think you ment mpg?

Lincoln · Apr 2, 2004

I used to get low 20's all the time with my 31's. It's been in the 15-18 range longer than I can remember.

You could put 215/75's on for the street, that would be cool. :dunce:

Christopher · Apr 2, 2004

I've never ran 4:10's but my AW4 with 4:56 and 31's I got about 18 now with 4:56 and 35's I get about 14-15.

sintax · Apr 2, 2004

Gas milage should NEVER be a consideration when you are talking about 35's. You kind of have to throw all of that out the window when you start considering things like that.

I am running 4.88's with my 33" TSL's, i'd HATE to have 4.56's, I dont know how you guys run em.

I do not even pay attention to how many MPG i'm getting, i'm sure i'd rather not know.

-Scott

ChuckD · Apr 2, 2004

sintax said:
Gas milage should NEVER be a consideration when you are talking about 35's. You kind of have to throw all of that out the window when you start considering things like that.

I am running 4.88's with my 33" TSL's, i'd HATE to have 4.56's, I dont know how you guys run em.

I do not even pay attention to how many MPG i'm getting, i'm sure i'd rather not know.

-Scott

Amen!

ZachMan · Apr 2, 2004

Christopher said:
I've never ran 4:10's but my AW4 with 4:56 and 31's I got about 18 now with 4:56 and 35's I get about 14-15.

Really? Do you do any hwy driving? I averaged 18 mpg stock (3.55s and 29s).

ZachMan · Apr 2, 2004

sintax said:
Gas milage should NEVER be a consideration when you are talking about 35's. You kind of have to throw all of that out the window when you start considering things like that.

-Scott

I understand, but right now it has to be with the way gas prices are going up. I'm in college and I drive home on the weekends so yeah going from $30 a week for gas to $60 a week makes some difference. Thats why I may go with a smaller tire, but probably not.

18 mpg w/ 31s and 4.56s? Hmm...

red87cherokee · Apr 3, 2004

I've got 4.88's and am still running 31's until I trim the fenders and install the 35's BFG AT's I have in storage. I started with 3.07's (5 speed manual tranny) and got 25 MPG with 235/75R15's, then I lifted it about 4 inches and put on the 31's and got abou 15-16 MPG, and now (with the 4.88's) my gas mileage has improved to just short of 20 MPG's - all of these mileage figures are with a corrected speedometer and for highway, only, driving.

The RPM's went up with the 4.88's, but the engine stayed in a better RPM range and I could use the OD 5th gear more effectively . . . so, contrary to popular opinion, lower gears CAN cause an improvement in MPG's.

FWIW: With the 4.88's, 31's and using 5th gear the engine spins at about 3,000 RPM's at 70 MPH.

ChuckD · Apr 3, 2004

There is a reason for this. Manufactures have to make there car more evironmentally friendly. So they may under gear a vechile so that it turns less RPM's down the freeway, but in turn may have lowered the fuel effiency. I think this is what they did with our Cherokees. So running your Cherokee down the freeway at 2500 RPM's is normal.

xjaddiction · Apr 6, 2004

4:56's, 35 SS TRXUS on a 10 inch rim, Warn hubs (disconnect on interstate), and no-slip in the rear, I'll get between 15 to 17 MPG running 70 to 75 mph with the cruise control on.

Greddy

CRASH · Apr 6, 2004

Our DD 1999 Xj gets 20.5 MPG. We run 100 miles round trip every day, at near 80 mph. 3.55's and 215's.

My rock rig runs 4.88's, 35's a one ton manual OD tranny, big axles, and a bunch of weight. Even with 205,000 on the 4.0, I manage 16 or so on the flats. In the mountains where I live, I may get 11 mpg, with a stiff wind behind me.

Tell Mom and Pop you just can't come visit as much as you used to, cause you got some new meaty meats.

CRASH

bburge · Apr 6, 2004

With a manual tranny, 4.10's and 31 MT's (AND an adjusted speedo gear to match my GPS readings) I get 13MPH.

Make sure that people who have changed all these items have ALSO added the appropriate speedo gear to go with that or their numbers are worth the time it took to type them....

bburge

CRASH · Apr 6, 2004

bburge said:
With a manual tranny, 4.10's and 31 MT's (AND an adjusted speedo gear to match my GPS readings) I get 13MPH.

Make sure that people who have changed all these items have ALSO added the appropriate speedo gear to go with that or their numbers are worth the time it took to type them....

bburge

Who needs a speedo gear when you have on-board GPS?

CRASH

Chilly · Apr 6, 2004

I have AW-4 with 4.56 gears and 35's and I try not to think about MPG. I just know that I have to fill up about every 10 days.

And as for 35's and 4.56 it is acceptable but I am planing on going lower when I swap out to some beefier axles.

Gas mileage with 4.56s/4.88s and 35s and 31s w/ 4.10s?

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