mpg rant

[Pete M]

:rant:

Ok, so I just read a post over at naxja from a guy wanting to get 4.10s to go with his 33s. He says he's worried about gas mileage and that he usually drives 75mph. Wait, lemme just paste it:

 

would i get better gas mileage with 4.10 with 33/12.50 opposed to 4.56. ive searched and everyone just says 4.56 or 4.88. but my main concern is gas mileage. i mainly cruise at 75 mph.

 

And then later on:

 

i do have the aw4. and the truth is that I'm usually running at highway speeds. the only time I'm not at that speed is when I'm offroad. and i live in the land of no hills. i just want the best gas mileage.

 

I can't STAND people who say they are worried about fuel mileage and then drive their shoebox Jeep on 33s at 75 mph. AAAAAA!!!!!!!! :rant: As if they either don't understand or think they can beat physics somehow. :fool: Your mpg is going to SUCK no matter what gearing you get. If you really truly cared about your mpg, then either slow the heck down, buy a dang car, or stop caring about your economy and go buy your gears/mufflers/airfilters/etc for other reasons, like "I want more power" or even "it's cooler looking". :D

 

We now return you to your regularly scheduled program... :nuts:

[Mitch]

[Mitch]

Oh and I take pride in knowing that with my TJ (daily driver) that my weekly gas cost and monthly payment on it more than cover the cost of a luxury car.... $#!& my monthly payment alone makes me think I should have a BMW or Viper out front of the house.... not a TJ lol... I got screwed at the dealership!

 

but it seems I always do, so no worries.

[Kenosha Warrior]

My 2.5L MJ is a slight hog, but an O2 and a nice tune up come spring

 

(dizzy cap, plugs, oil change and o2) I should be running nice again.

[JeepcoMJ]

gas mileage and big tires...go with a 3-something. the guy's dumb.

 

I've got 3.72 or 3.73 gearing in my truck i guess, and with 31x10.50 tires and my camaro engine, i'm getting 20 mpg at speeds of 65 to 75 mph. the trick is to keep the RPM's low...which isn't all that easy if you have a 4-banger or a 2.8. the 4.0 and 3.8 camaro engines have more than enough power in 5th gear/overdrive to coast along. it just takes some gentle driving to get mpg outta it.

 

but on the same notion, Pete is correct 100% about bigger tires = worse gas mileage. that's FACT and the guy should just live with it or go buy a f*ing kia.

[feerocknok]

People think my gas mileage would be good because I have a 2.5. When they ask what sort of mileage I get, I tell em it's a Jeep.

[JeepcoMJ]

well kassidy if your engine ran right...maybe you'd get some gas mileage. that 24 seconds to 60...wow. i'm actually impressed believe it or not..

[Oizarod115]

well, 4.10s will get a decent 18 at 75... my brother is running 4.88s with an AW4 and 35s and when the speedo hits 85 the revvs are at 3k... (which 4.88s and 35s his speedo runs a little fast)

 

you can't expect more than about 15 from a 4.0 pushing big tires. shoot. i get 17 STOCK. with a 5spd.

 

I'm with mitch shut up and get one of these...

[JeepcoMJ]

or buy a renault cherokee or comanche. my dad's gets anywhere from 25 to 35 mpg depending on weather and driving. i think the worst he's ever gotten was 21 mpg with that thing pushing 27" tires with a cracked precup on the head and in 4wd pulling a trailer.

 

those lil 4 cyl renaults get damn good mileage...but they're a terror to keep together unless you know what you're doing (we've learned..)

[feerocknok]

well kassidy if your engine ran right...maybe you'd get some gas mileage. that 24 seconds to 60...wow. i'm actually impressed believe it or not..

I got 24 mpg on my last tank, but my Suzuki friend gets 35ish in his 4-cyl (1.6 or something though, and much lighter), so all my buddies think 4-cyl = 30+ mpg.

 

I'm surprised that Camaro engine keeps that sort of mileage! Must be the fuel injection? It is TBI?

[JeepcoMJ]

nope, it's MPFI. I got 22 mpg on my first tank with the new engine. If you drive it right in a camaro they get up to 30 mpg highway..but with a heavier car, bigger tires, and 4wd I think I'm doin good at 20 to 22. haha, when we had all this terrible weather, I was driving it to and from work (45 min.) in 4wd @ 45 to 50 mph and still getting almost 15 mpg!

 

love it!

[jared]

sorry pete, but gas milege concerns me too. i owned 5 hondas in the past so 37 mpg or more was common for me, now i get about 9 around town in the jeep.

 

but i don't cry about it. i do want gears for performance and slightly bettr mileage, but mileage is secondary to me now.

[Bonkers]

[edit] - sorry, I was reading too far ahead and made this post off-topic. Didn't mean to hi-jack ya Pete... :cheers:

[Pete M]

Oh, don't get me wrong, you can care about mileage. I care about mileage to a certain extent (towing a trailer on the freeway and getting 27 mpg in the CRD is fun :D). But if you're whining about gas mileage and you're not willing to slow the heck down...

[86FUBAR]

When me and my buddy drove out NC to go to school , me in my 75 ramcharger 4in on 33s 3 speed and a verry healthy (thirsty)360 i got 6-8 (on a good day )mpg i didnt complain one bit , my buddy in his 96 dodge wit 6in 35s auto he was getn 12-14 mpg and he cried the entire way ,all 2800 miles i allmost turned and went home. can't stand people that complain bout stuf like that . u drive a truck deal with it!!! :headpop:

[87manche]

3.73's and 31's with a 5spd and 4.0 net me 22MPG on the way back from flatnasty, with so much weight in the back I had the tires aired up to 45 PSI.

Average cruise was over 75, as we did 684 Miles in 9 hours 30 minutes, with 2 fuel stops.

it's possible, ou just gotta tune it well.

 

As to the keep the RPMs low, not quite, a 4.0 is most effeicient at it's torque peak, somewhere abouts 2500. I ran between 2500 and 3K RPM the whole way from MO, my foot lightly on the gas, with good manifold vacuum the whole way.

manifold vacuum is the best indicator of gas mileage and how hard you're working the motor, not the RPMs it's at.

[Pete M]

As to the keep the RPMs low, not quite, a 4.0 is most effeicient at it's torque peak, somewhere abouts 2500. I ran between 2500 and 3K RPM the whole way from MO, my foot lightly on the gas, with good manifold vacuum the whole way.

manifold vacuum is the best indicator of gas mileage and how hard you're working the motor, not the RPMs it's at.

 

:agree:

[JeepcoMJ]

lol, when i say low i mean 2k to 2500. i have a dif. engine than you too keep in mind. but mine performs best at around 2000 rpm when doing 65 mph.

[87manche]

well, you're far from factory, hence the disclaimer about the 4.0.

 

But al engines work most effieciently at or near the torque peak, and manifold pressure is still the best way to measure a motor's effieciency at a glance.

I'm likely going to install a manifold pressure guage. Not only is it good for gas mileage monitoring, but it will also alert me to any serious damage done to the motor, perhaps before I destroy it completely.

[Duner]

Gas mileage?

 

When it was 2wd 3.07 on 26" tires 17 to 18

4wd on 29" 3.07 gear front shaft not in yet 14 to 15

4wd on 29" 3.55 gear front shaft not in 15 to 16

4wd on 33x12.5 3.55 gear shaft in place 14 to 15

 

If it holds 15 with the 4.10s that will be great but i'm only interested driveability the truck felt good with smaller tires now it feels under powered.

 

By the way my dad's 05 tj with 3.07 gear and 32's gets 13 to 15 with a 6spd manual (Its a jeep thing) and if we need to get gas mileage we take my mom's 05 malibu 36 to 39 on the hwy 4cyl 75mph with a/c.

 

So suck it up or sell it I am an oil company spokesmen.

[Maveric]

I average 65mph and get around 20-22 mpg, my dad in his xj driving from Seattle to Sacramento got up to around 24-26 mpg.

So yeah I agree with the rest of y'all, my '85 Audi 4000 got over 30 in its little 4cyl engine, it was a fun car to drive, had performance for a 4cyl but I don't expect my truck to do that well, for one its a truck, two its bigger then the Audi, and three it can offroad, four its got a bigger engine.

You want to save gas, buy an Audi or something, you want to actually take something offroad once in awhile, buy a jeep and loose the extra wee bit gas.

 

:cheers: here's to the jeep, and the Audi that I sold to get it.

 

Jeep on!

[mjeff87]

and that's why I drive a ghey Ford Escort as a DD....gets 32-35 mpg mixed, damn near 40 on roadtrips. I've long since given up on efficiency with the MJ, especially since the 4WD conversion and locking the CAD motor.

 

Interestingly, though..I seem to be getting better mileage with the 4.56's now. It's too early to call it (haven't even ran a full tank of gas thru it) but the needle doesn't seem to be moving as far south as quickly as it did with the 4.10's. I've got a mini-roadtrip maybe this weekend, about 200 miles roundtrip, so we'll see for sure what effect the gears did. Weird, but deeper gears seem to increase my mileage :nuts: (but I haven't swapped my speedo gear out yet, and that does have an effect).

 

Jeff

[Pete M]

Lower rpms does NOT necessarily equate to lower gas consumption, so you may have simply put the engine into a better power range. :D

[87manche]

Lower rpms does NOT necessarily equate to lower gas consumption, so you may have simply put the engine into a better power range. :D

exactly. I get way better mileage with 3.73s than I ever got with 3.07s.

I'm turning the 4.0 up a bit, and it's noisier, but you can't argue with 22MPG at 75-80 MPH carrying the load I was in the bed.

[reddog]

Wow 22mpg , I'm lucky to get 12-15 and all I got are some 31's on it. I'm changing the axles from 3.07 to 3.55 in the near future hopfully I get a couple miles back. I'm not complaining I get on it once and a while, but the highway sucks it down fast it bogs down at 65 70mph especially when I got a head wind or going up a hill it kills it, I loose mph's fast. I try to draft people to help it some.