Auto vs 5sp MPG difference?

Hello,
In two identical vehicles, driven the same, could one expect a noticeable difference in MPG between an auto and a AX15?
Thanks,
MIkel

Your US Government calculated all that for you and put it right all here in a fancy chart -> http://www.fueleconomy.gov/feg/bymodel/1999_jeep_cherokee.shtml

YMMV.

It's a good question, and one I've wondered about, but never been able to test very well because all my Jeeps have been different years. Of the three I've owned, and a couple of others in the family, the best mileage award goes to my 87 AW4, which got a pretty consistent lifetime average of 23. I replaced that with a 95 AX15, which over the 150 thousand plus miles I put on it, rarely topped 20. I replaced that one with a 99 AX15, which in the hundred thousand + miles I've driven it so far, has fallen somewhere between, peaking at about 25, dropping easily into the teens, and averaging 20-22 for the most part. My stepson had a 93 AW4, and got about 20. My son had a 96 AX15, and got about 24.

In other words, I don't really know, but I think it's going to be pretty close.

One of the paradoxical problems with the manual models is that they're geared so tall that they are not in their optimal torque range when cruising. I know some people have contended that you'll get better overall mileage if you stay in fourth gear more, but I haven't done a really scientific experiment on that.

Tim_MN said:

Your US Government calculated all that for you and put it right all here in a fancy chart -> http://www.fueleconomy.gov/feg/bymodel/1999_jeep_cherokee.shtml

YMMV.

Click to expand...

I wouldn't trust those charts much.

My all city commute in my '05 Liberty CRD gets me 25mpg tank after tank (off GPS), while the site above lists it at 19mpg :dunno:

As I noted YMMV, but the comparison of relative efficiencies between 4 cyl or 6 cyl, and auto or manual trans still is correct.

Have about the same experience as Matthew. Wifes stock 89 AW4 gets a steady 23-24 mpg, my 94 AX15 18-20 with 30-9.50s and 3.55 gears

And my 00 w/auto and 29" tires averages about 18 mostly highway driving while my brother's 97 but otherwise basically the same averages about 20 and that includes running up 95 toward DC.

99 4.0l 5 speed 4x4 np231 8.25 rear, stock tire size,3.07 gearing, 19 city, 23 highway (75 mph) average. I feel like with all the torque of the 4.0L and good conservative shifting you can smoothly shift well below 2,000 RPMS and achieve great number for gas mialage. Also I dont know how it is for the aw4 but with the ax15 with stock gearing you dont cross 2000 rpm on the highway until like 72~73 mph

When I had my 95 4.0 8.25 2wd gearing unknown, stock tires. To my knowledge the motor was in tip top and I tried driving conservatively but never could accomplish more than 16 in the city and 18 on the highway

Matthew Currie said:

One of the paradoxical problems with the manual models is that they're geared so tall that they are not in their optimal torque range when cruising. I know some people have contended that you'll get better overall mileage if you stay in fourth gear more, but I haven't done a really scientific experiment on that.

Click to expand...

I installed a overhead in my jeep, 4th gear at 70 mph gets much less than 5th. But then again I don't know what variables you were questioning.

I hit 23mpg highway in my MJ with 3/4 ton of junk in the bed, 91 4.0/AW4 with 230 thousand miles on it and no rebuilds.

I now get around 13-16, but it's now undergeared (AX15, 3.55s, 33" tires), lifted, big tires, and has a hole in the exhaust the size of a nickel right above the O2 sensor that I haven't fixed yet. So that's not much of a surprise really. When I gear it better I expect it to go back to more like 20.

ktwalker01 said:

I installed a overhead in my jeep, 4th gear at 70 mph gets much less than 5th. But then again I don't know what variables you were questioning.

Click to expand...

Definitely at freeway speeds you want to be loafing along in fifth. The qray area is on local roads where speeds are in the 40's and 50's, especially when the terrain is rolling. You can stay in fifth, but maintaining speed then requires a pretty heavy foot, and it's been asserted (not scientifically tested by me) that you'll get less vacuum drop and better economy if you stay in the 2000 rpm range. I am too lazy to test this, and I'm so used to short shifting that it would be a hard habit to break anyway.

Of course, that makes perfect sense. Once you drive a particular stick shift car for a while you tend to realize what gear it wants to be in at that given time / scenario.

I have 30's on mine, I get about 15 around town and 24 highway. Stock gearing, ax-15