Gas Mileage

What are some ball park city mpg numbers for these jeeps? I realize they aren't economy vehicles, but they don't weigh that much either.

Here are my guesses:

4cyl - 15-18 mpg
6cyl - 14-16 mpg
8cyl - 12-15 mpg

I really want to build a flatfender or early CJ 5, but I'm trying to figure out how to justify it to my wife. If it can get better city mileage than my Grand Cherokee I might have a leg to stand on.

I would probably run a completely stock drivetrain, or I would do a 4.3/5.7 TBI, sm465.

Your thoughts on a setup that can make a short in-town commute (no freeways), get better than 15mpg in the city, and still do most of the trails in Moab?

 

early cj's didnt come with v-8's.
i saw a write up on novak's web site where they stuck a 400 hp vette motor in a jeep and it got better mileage than a stock 4.0. so stock isnt neccessarily good. mine is down right now or i would give ya stats.

 

CUmmins 4 bangers are supposed to get 30 or better. Of course they are heavy and expensive, but are great little motors. I have seen write ups on the web about this, but have no experience with it. I would really like to see this setup done in an early or intermediate.
30 miles per gallon with lots of torque would be awesome..

High5

 

I'd expect some of the Cummins mileage is due to the limited top speed. You're always pushing a lot of air with a Jeep, and that makes the fuel mileage very speed sensitive. You can probably get 20 mpg from an F4 if you keep the speed down to 45 or so (that's 56% of the wind resistance at 60). It's a very steep barrier.

 

Thanks for the quick replies.

Sparky, thanks for the link. I had already searched quite a bit, and apparently under the same terms that you pulled for me because I had already read most of those threads.

I don't think I would log enough miles to make the 4bt worthwhile.

I realize that early 5's and flatties didn't come with v8s, but a lot of vehicles that are available these days have been swapped.

Novak's article is what got me thinking. More than likely I will end up with a Tub/Frame with no engine and so I'm trying to decide what drivetrain I would want. The buick v6's seem to be pretty popular with this crowd. I would really like fuel injection, however.

Any more thoughts or figures?

 

If mileage is your main concern, the 150 cid inline 4 from a Wrangler or the last of the CJs would make a good swap. It's a very reliable engine that came from the factory with both throttle body and multiport injection. The Chevy 153 cid I4 is also a popular swap for CJs. However, reducing the displacement will have diminishing returns in mileage, especially if you end up pushing the smaller engine hard all the time to make up for the reduced performance. Reduced displacement along with appropriate driving habits will improve mileage, but you can only take that so far till it becomes impractical.

The V6 is popular becasue it fits in the engine bay so well and makes lots of power for its size. It can be fitted with fuel injection.

 

so I guess a spring over and 35's aren't going to help the issue..

The good part is that my commute is short and the highest speed limit I see is 45mph.. and that's only possible when there is no traffic, so speed is relatively low throughout the commute.

I think I may be able to sell this to my wife. Thanks for all the help.

 

I have a 350 with the 5:38's and get 8 mpg

 

One other thing to think about is the goal is not the turn the least number of RPMs but to have your cruising speed be in the powerband of your motor( preferably low part of the band)

 

you want power and mileage? get the even fire v6 from a 79-84. they came with turbo's and were extremely under rated at 200 hp/300 ftlbs. ive got one sitting in my garage that ALMOST went in my jeep, but i stuck with the odd fire..>=)
you can mount a holley or TBI setup on top and get good hp when needed and great mileage (and smoke em down when needed)

well..its an idea anyway..=)

 

1955 cj5 134 f 20 mpg in town just like the the book said

 

You could probably improve gas mileage by tieing down the windshield and wearing a motercycle helmet
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note: actually have a helmet in garage, but not quite crazy enough yet...

 

One word - Diesel!

OK a couple more, I can pull 19 mpg out of my K3500 will 4:10 gears!

 

Since I drive about 15 miles a day, it would take me (by my guestimation) about 16 years in fuel savings for the diesel to pay for itself. If I was planning on driving more, then maybe I'd consider it.

Our other car is a diesel, a VW Jetta TDI. Diesels are fantastic, but there isn't a cheap way to get a good one in a Jeep.