Mpg?

[AlamoCJ8]

OK, don't kill me here just hear me out.

I have a new position with my company that has moved me from working from my home to working in a office that is a 50 mile round trip every day. I am driving my 1985 Scrambler with 78K original miles daily. I love my Jeep and want to keep it. My problem, the Jeep gets around 9 mpg and it burns almost as much oil as gas. I have factory auto and air and want to keep both though not necessarily factory but the factory look. With me so far? What I need is a new motor and if necessary Transmission that will significantly improve my gas milage. My goal is mid 20's and if necessary I am willing to even give up my 4wd capability to keep the Jeep. I hope that isn't necessary but again, I don't want to loose my Jeep but I want my house more. Thoughts, diesel, 4cyl, hy-bryd, electric? Go crazy, no idea is off the table...

Thanks for the help,

Tom

 

[ThisGuyUKnow]

I hear that Diesel swaps can get FSJs up into the 20s so I would imagine that would be your best bet.

 

[hole]

Wow, 9mpg is pretty low for a AMC 258 i6 / 4.2l . I have no experience with an auto Transmission , but I get 16-17 mpg out of my 8 with a T-5 Transmission . Except for Mopar MPI it's all stock with 111k on the clock. As for a engine swap, unless you have a cheap source for the donor, it might be just as cheap or cheaper to look for a 4cyl commuter car to drive to work and not chop up a rare 8.

 

[Busted Knuckles]

This is a troublesome query, because the combos are endless. If you're interested in the path of least resistance, you need EFI and a Auto with Torque converter clutch and Overdrive (which you wont find any other way, but thats an important part of the equation).

A Cummins 4BT would be a natural swap, and its been done many times, as well you will find a forum or two that cover that swap alone.
You must like the smell of raw and burnt diesel for that to work out, plus the sound. I love diesels, own 3, but wont put one in my jeep, but I dont drive it as daily driver, and I dont want to smell it when crawling on a trail, (or listen to it for that matter).

My 91 XJ 4.0L HO with CA emissions gets 25+ on the highway, and does pretty good bombing around town, but its got a 5 speed (manual) with 200k on the clock and is using a little oil. If you want to go cheap, Id consider a 4.0L, out of a XJ or ZJ complete with a chrysler O/D Transmission . Not sure what kind of hit youd take for the auto, but it shouldnt be more than a couple MPG. Stay away from the AW4 Transmission though...

The other option is a 5.3L LSx motor out of a 99-up Silverado/Sierra with the 4L60E. My 99 1500 P/U would pull 20mpg on the highway, it was a 2wd std cab, with an 8' box and contrators topper on it. I bought it new, put a 100k on it, very reliable, the only repair was the fuel pump. I miss the truck, but now drive a newer version.

Thats my 2 cents if I where "wearing your shoes", and I wish I was, Id love to own your scrambler ! Texas truck with 78k must look nice !

 

[DHugg]

Wow, 9mpg is pretty low for a AMC 258 i6 / 4.2l . I have no experience with an auto Transmission , but I get 16-17 mpg out of my 8 with a T-5 Transmission . Except for Mopar MPI it's all stock with 111k on the clock. As for a engine swap, unless you have a cheap source for the donor, it might be just as cheap or cheaper to look for a 4cyl commuter car to drive to work and not chop up a rare 8.

I used to drive a '78 Grand Marquis with a 458 that got 16 mpg....... eight on the road and eight in town! I'd rather drive my Jeep AMC 304 at 10mpg, and just not travel as much or as far. Looks like that may be the future for most of us.

I feel sorry for some folks whose commute is "doin' 12 to make 8". There is a point of diminishing return on burning 4 hours of gas to make an 8 hour paycheck. I did it for two years, living like a robot. Wouldn't do it again!

 

[jarbidge09]

I put fuel injection in mine and an Overdrive get 22-23 mpg.

 

[73jeep]

I'll probably get flack for this but the 4bt is a unrefined dinosaur, heavy, mechanical injected, and louder than all get out. Plus people think they are made of gold, so they have a high price tag. A Mercedes Benz diesel is a slightly better choice but the adapters are expensive.
Don't get me wrong i love diesels (my gf just bought vw jetta tdi), but your ROI for this swap is going to be a long time.

If a cheap commuter car is out of the question, i would swap in a 4.0L and ax15 manual Transmission . The 4.0L bolts right in and the ax15 bolts up to the Dana 300 with minimal mods. This should net you around 20mpg.

 

[ThisGuyUKnow]

This is a troublesome query, because the combos are endless. If you're interested in the path of least resistance, you need EFI and a Auto with Torque converter clutch and Overdrive (which you wont find any other way, but thats an important part of the equation).

A Cummins 4BT would be a natural swap, and its been done many times, as well you will find a forum or two that cover that swap alone.
You must like the smell of raw and burnt diesel for that to work out, plus the sound. I love diesels, own 3, but wont put one in my jeep, but I dont drive it as daily driver, and I dont want to smell it when crawling on a trail, (or listen to it for that matter).

My 91 XJ 4.0L HO with CA emissions gets 25+ on the highway, and does pretty good bombing around town, but its got a 5 speed (manual) with 200k on the clock and is using a little oil. If you want to go cheap, Id consider a 4.0L, out of a XJ or ZJ complete with a chrysler O/D Transmission . Not sure what kind of hit youd take for the auto, but it shouldnt be more than a couple MPG. Stay away from the AW4 Transmission though...

The other option is a 5.3L LSx motor out of a 99-up Silverado/Sierra with the 4L60E. My 99 1500 P/U would pull 20mpg on the highway, it was a 2wd std cab, with an 8' box and contrators topper on it. I bought it new, put a 100k on it, very reliable, the only repair was the fuel pump. I miss the truck, but now drive a newer version.

Thats my 2 cents if I where "wearing your shoes", and I wish I was, Id love to own your scrambler ! Texas truck with 78k must look nice !

what is the gear ratio and tire size on that xj? I converted my AMC 258 i6 / 4.2l to 4.0 head/injection and installed and ax15 and was hoping to see 18-20 mpg hwy but didn't. i am running 31s and have 2.72 gears though.

 

[73jeep]

what is the gear ratio and tire size on that xj? I converted my AMC 258 i6 / 4.2l to 4.0 head/injection and installed and ax15 and was hoping to see 18-20 mpg hwy but didn't. i am running 31s and have 2.72 gears though.

That figures out to be 1500 rpm in top gear, thats a little low. 1900-2100 is better. Try a run with 4th gear.

 

[IOPort51]

2.72:1 ratios will get you the mileage. wouldn't use bigger than 31 inch tires.

 

[Busted Knuckles]

what is the gear ratio and tire size on that xj? I converted my AMC 258 i6 / 4.2l to 4.0 head/injection and installed and ax15 and was hoping to see 18-20 mpg hwy but didn't. i am running 31s and have 2.72 gears though.

You know, off the top my head I don't remember, but its very low numerically, under 3.00 to 1. The thing idles at 10 mph (way too fast for wheeling), and its got stock size Goodyear rubber on it. I use it as a car, and I dont drive it hard.

The EPAs revised numbers for my XJ are 15/20. But they dont account for different final drives, as well mine does have CA emissions, dont know if they run any leaner or ?

I would expect if you dropped my power train into a CJ, it would get a little less MPG just because of the "profile" of a Cj vs. the Cherokee, mine is also a 2dr sport, so its shorter and lighter than a loaded "Limited " 4dr.

 

[chris insull]

OK, don't kill me here just hear me out.

I have a new position with my company that has moved me from working from my home to working in a office that is a 50 mile round trip every day. I am driving my 1985 Scrambler with 78K original miles daily. I love my Jeep and want to keep it. My problem, the Jeep gets around 9 mpg and it burns almost as much oil as gas. I have factory auto and air and want to keep both though not necessarily factory but the factory look. With me so far? What I need is a new motor and if necessary Transmission that will significantly improve my gas milage. My goal is mid 20's and if necessary I am willing to even give up my 4wd capability to keep the Jeep. I hope that isn't necessary but again, I don't want to loose my Jeep but I want my house more. Thoughts, diesel, 4cyl, hy-bryd, electric? Go crazy, no idea is off the table...

Thanks for the help,

Tom

IMHO, there's no point in giving up the 4WD with so many resources out there that support various engine/ Transmission options, from mild to wild. I would think that with a stock rebuild and an OD Transmission you could approach your MPG goals. Provided you've got the gear ratio to support an Overdrive ... A lot of factors come into play with MPG, and our CJ's aren't known for aerodynamics.

 

[ThisGuyUKnow]

I would expect if you dropped my power train into a CJ, it would get a little less MPG just because of the "profile" of a Cj vs. the Cherokee, mine is also a 2dr sport, so its shorter and lighter than a loaded "Limited " 4dr.[/QUOTE]

Wait are you saying you get slightly better mileage because your xj is not shaped like a big piece of toast?

 

[IOPort51]

My truck gets 20 and my cj gets 14. the only difference is the truck is heavier and has 2.73 R&P's and the cj has 3.58's.
You need the most bang for your buck, spending 3 or 4 grand on the CJ to get another 5 MPG may not be the most economical move you could make.

One of my favorite jokes is the guy that buys a new Harley for the gas mileage.

 

[ThisGuyUKnow]

My truck gets 20 and my cj gets 14. the only difference is the truck is heavier and has 2.73 R&P's and the cj has 3.58's.
You need the most bang for your buck, spending 3 or 4 grand on the CJ to get another 5 MPG may not be the most economical move you could make.

One of my favorite jokes is the guy that buys a new Harley for the gas mileage.

I have a Honda 919 and it gets anywhere from 34 to 42 mpg. The issue with using the bike to negate fuel cost is I find myself joyriding and taking the long way home so although I use like 3x less gas I end burning through it almost as fast.

 

[Busted Knuckles]

I would expect if you dropped my power train into a CJ, it would get a little less MPG just because of the "profile" of a Cj vs. the Cherokee, mine is also a 2dr sport, so its shorter and lighter than a loaded "Limited " 4dr.

Wait are you saying you get slightly better mileage because your xj is not shaped like a big piece of toast?[/QUOTE]

Yes, basically...toast, I like the analogy of a "billboard", on a related note, my daily driver is a 2005 Yukon XL (suburban) 4x4, its loaded, 6.0L gas motor. I get 14.5 MPG higway on a perfectly still day, as in no wind, Ive gotten as little as 7 MPG driving into a serious head wind at 55 mph. Ive also gotten as high as 20 MPG with a serious tail wind. Its interesting how much "drag" that thing has.

 

[dave123]

Some ideas:

1. buy a cheap car that gets great MPG and use the Jeep less (that is what I did).

To get the jeep better MPG, there are a million things. Here are a few:

Tuneups alone can add MPG to most engines. Clean/rebuild fuel systems. New air filter. Upgrade ignition (I did the Team Rush and got 3 MPG improvement). Check air pressure in tires. Smaller tires, gearing, getting a tranny with another gear for highways. Are brakes dragging? Is the tranny slipping? Are emission controls working properly? Is you catalytic converter clogged (this can be a biggie)? A free flow exhaust with headers will give more power and better MPG (you won't have to get on it as hard to move).

I would consider the return vs the investment. For example, if you spend X amount $$ to get X amount extra MPG, will the money saved at the pump cover the investment? Putting in a diesel engine could get expensive, how much will it save, how much power will you lose? Is it worth it...

Good luck

 

[ThisGuyUKnow]

a fuel injection system of some sort will improve the economy.

 

[kickitandholdit]

Electric would be cool but the cost of batteries would slap the S*** out of your wallet and the lack of information could put you in a black hole.

I think your best bet would be sending me 3k and ill send you a computer chip that makes everything down hill and you can roll everywhere you go or buy a scooter that gets 85mpg

personally i like the diesel idea

 

[54cj3b]

Simple solution :

Buy a cheap 4 banger for commuting youll get better gas mileage and not have to worry about a major engine swap
you could prob find a cheap 4 banger for almost 1/2 of what it would cost to do a transplant