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  #21  
Old 01-26-2012, 09:12 AM
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derf derf is offline
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The biggest things to improve mileage:

1. A good tune up. You'd be surprised how much even just a fresh set of plugs can help. Updating the wear parts (like springs in your distributor) as part of a full tune up can make a drastic difference in mileage all by themselves.

2. PROPERLY tuning your carburetor. Spending a couple of days with an air/fuel gauge hooked up to the exhaust and a vacuum gauge while you swap jets, meetering rods and springs will get your engine running better than any of the other shade tree advice.

3. Once you get your carburetor truly dialed in, you can do the most important thing that helps mileage. Drive with a lighter foot. When your carburetor is tuned properly, you don't have to push the throttle as far down. If you're running rich or lean, you have to push the throttle open father to make the same power as when you're running with the proper tune. That's what gives you the best mileage.

4. Of course, you can see minimal gains by running synthetic lube, open hubs in the front, etc. But all told those won't amount to very much.

If you want to get beyond that, you have to start looking into major modifications that won't pay for themselves for years. Things like fuel injection, axle gear swaps and overdrive transmission swaps will help your mileage but they cost a lot and take a very long time to pay for themselves.
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Last edited by derf : 01-26-2012 at 09:16 AM.
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  #22  
Old 01-26-2012, 10:34 AM
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fulsizjeep fulsizjeep is offline
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Quote:
Originally Posted by fulsizjeep
In 03 when my GW had 225K on the original engine, 4" lift, 33s, 3.73 gears, all emissions removed and basic vacuum connections only with MC 2150 - I was getting about 10 mpg. When it had 95K on it, no lift and had all the emissions, I got 16 mpg on the highway most days. In 04 I lost compression in #2. I spent about $1700 putting a 40K mile 401 in it (new cam, TC set, SP2P intake, AFB). With the best tune I was only getting 9.5 on the highway.

What does this mean? I got a 401.
carrying this to the next chapter...

By 07 my 727 was a slushy POS. I took a 81 lockup 727 to a very reputable rebuilder and replaced the POS. Gas mileage went from 9.5 to just over 11 on the highway. Yes, rebuilding a slush box and replacing TC can do that.
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88 GW, 401/727/208, 5" lift, D44s/4.10s/locked up, 35s and a few Evil Twin mods, http://eviltwinfab.com and a few TT's Fabworks mods, http://www.ttsfabworks.com
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  #23  
Old 01-26-2012, 11:35 AM
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hummer010 hummer010 is offline
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Quote:
Originally Posted by fulsizjeep
carrying this to the next chapter...

By 07 my 727 was a slushy POS. I took a 81 lockup 727 to a very reputable rebuilder and replaced the POS. Gas mileage went from 9.5 to just over 11 on the highway. Yes, rebuilding a slush box and replacing TC can do that.

Recently I changed the tranny fluid in my '04 GM and gained about 1 mpg average. The change was long overdue, but I didn't expect to see that much of a difference.
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  #24  
Old 01-26-2012, 11:37 AM
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Suddendeath Suddendeath is offline
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I get about 12-13 MPG with 33's and 4.10's, HEI, emissions delete, holley 670 truck avenger, eddie intake, stock exhaust manifolds. I just never really hop on it. I have an in-cab vacuum gauge and I try to keep the needle as close to 20 as possible when driving, and I never let it get lower than 10ish.

Though the best gas mileage I ever got was 35mpg when the jeep was parked and I was driving the Saturn
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  #25  
Old 01-26-2012, 11:57 AM
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bmoose bmoose is offline
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Milage improver ver 2.1

Anything you can do to take load off of engine... electric fan, remove AC compressor and or smog pump.
Carb tuning as mentioned before. That is becoming a lost art.
Synthetic lubes, as mentioned
Proper tire pressure.
Light foot on go faster pedal
Cold air intake and good filter
TFI ignition upgrade, wires & plugs
good exhaust ( not always headers but reasonalbe straight pipes & hi-flow muffler)
aerodynamics ( yes these go thru the air like a brick) but following someone on the highway does help. why does nascar call it drafting?
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  #26  
Old 01-26-2012, 12:13 PM
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Suddendeath Suddendeath is offline
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Quote:
Originally Posted by bmoose
Anything you can do to take load off of engine... electric fan, remove AC compressor and or smog pump.
Carb tuning as mentioned before. That is becoming a lost art.
Synthetic lubes, as mentioned
Proper tire pressure.
Light foot on go faster pedal
Cold air intake and good filter
TFI ignition upgrade, wires & plugs
good exhaust ( not always headers but reasonalbe straight pipes & hi-flow muffler)
aerodynamics ( yes these go thru the air like a brick) but following someone on the highway does help. why does nascar call it drafting?

The AC compressor runs on a clutch setup, so when the AC isn't on it just freewheels with virtually no resistance. If you're driving around with the AC off, you'll see the same gain as if you yanked the compressor.

That's another point to bring up. What was the study that mythbusters did, that under 50mph it's more efficient to have the windows open and over 50mph its more efficient to use the AC? With our trucks and our Great Googley Moogley aerodynamics, I'd think it helps even more at high speed to have the windows closed.
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  #27  
Old 01-26-2012, 12:23 PM
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Herk Herk is offline
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Point of reference, my 83 consistently got 14-15 highway, and 10-12 otherwise. Rig had Performer carb and intake, mild cam, more compression, headers, duals, 31" tires and 3.31 gears. That was also after some time spent tuning.

It would help to know more about what you have now setup wise. Tire size, gears, engine, exhaust, rig specs in general. What have you done so far?

Unless your rig has something wrong (howz the transmission?) or a Quadra-Trac you should be doing better.
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  #28  
Old 01-26-2012, 12:26 PM
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Snow Descent Snow Descent is offline
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Higher compression?
Might require efi and computer controlled ignition to see big gains.

I bought an econobox once 10 plus years ago and it killed my 69 Chevelle, which is still patiently waiting to be noticed in it's parking spot.
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  #29  
Old 01-26-2012, 12:42 PM
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capdaddy222 capdaddy222 is offline
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If you put bigger tires on you need to account for that in the odometer readings. Unless you changed your speedo gear you could be in the neighborhood of "normal" and just reading low miles per tank.
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  #30  
Old 01-26-2012, 12:52 PM
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sXeMike sXeMike is offline
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I used to get 15-16 highway as long as I kept my foot out of it. City driving dropped it to under 10. 78 wt, buick 455, 760 edelbrock, 35" all terrains, part-time qt, 3.54 gears.

A simple tune up will make a big difference....all of the little things add up.
Gears, tune up, part-time/full-time, weight, tires, etc.
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  #31  
Old 01-26-2012, 02:23 PM
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Stuka Stuka is offline
 
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The single best way to get better fuel economy is to change your driving style. If you are always using the secondaries, you are going to get horrible fuel economy. If you drive it nicely, accelerate slowly, try to carry momentum, etc, you can get much better economy. I used to be able to get close to 14 out of my old cherokee, and that was with a 6" lift 33's, bumpers, safari rack, etc. But then if I drove it to "have fun" I would get 10 or so.

Same goes for my J10. When it was bone stock, I could get 17 out of (its a i6 with a 4sp though).

Now obviously there can be mechanical limitations. I certainly would not remove the performer intake. The better flow that it provides increases efficiency which in turn leads to more power, which can lead to better fuel economy if driven properly.

I think the second biggest hit to fuel economy is tires. On most of my Jeeps, I take a 1-2mpg hit with mud tires compared to street tires.
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  #32  
Old 01-26-2012, 08:48 PM
TDHofstetter TDHofstetter is offline
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Driving style, definitely #1. If you drive leadfoot, you'll get abysmal fuel efficiency in anything. If you drive with a lot of thought given to fuel efficiency, you can easily get MUCH better gas mileage.

Manual transmission - I second that one (I don't remember who got to it before me). If you don't have a lockup torque converter, an automatic transmission is always throwing away fuel converted into heat inside that blasted torque converter.

Minimize your phantom fuel drains - anything electrical or driven by a belt cuts into your fuel bill. Heck, that even includes your FAN (the one at the radiator) unless it's electric. Even a clutch fan eats more gas than it oughtta', though that viscous coupling. I've run vehicles for years with no belt-driven fan at all, just an electric fan hangin' on the engine side of the radiator, controlled by a simple snap switch on the upper radiator hose. Above about 35mph, it NEVER TURNS ON unless I'm really workin' the motor hard. In stop-and-go traffic it sees a workout.

Good stiff hard tires, not ideal for safety, are better for fuel efficiency.

Disregard the engine swap suggestions - that's very seldom a good economic choice. It's very seldom that an engine swap actually results in better fuel efficiency, because most of these motors (when they're properly tuned and all other factors equal) run just about neck-in-neck for fuel efficiency. Your aerodynamic profile makes a LOT of difference... and that's not something you can easily change. Oh, but... if you have a roof rack... TAKE IT OFF. That eats more mpg than you'll BELIEVE, because of the turbulence around it.
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  #33  
Old 01-26-2012, 09:09 PM
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KansasWoody KansasWoody is offline
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Quote:
Originally Posted by The Colonel
Park it and buy a 4 cylinder econobox.

No seriously,

Park it and buy a 4 cylinder econobox.
X2!
I have a 1989 Honda Civic that gets close to 50 mpg I use as my DD, and when it's warm out, I DD this bad boy:
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  #34  
Old 01-26-2012, 09:29 PM
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Rich88 Rich88 is offline
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Stock manifold, ignition, 2150, EGR, exhaust & 727 and tire size gets me 12 highway and 10-ish around town on my '88. So something's clearly amiss. Don't accept it and keep trying.

But for starters, try fastening the carb secondaries in place and see how much of it may be your driving habits. A little zoom-zoom here and a little zoom-zoom there adds up over a tankful.
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  #35  
Old 01-26-2012, 09:50 PM
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  #36  
Old 01-26-2012, 09:59 PM
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  #37  
Old 01-27-2012, 02:39 AM
Indy48 Indy48 is offline
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I would love to be able to properly tune my carb, but I don't know how. I guess I could buy a book on it? I don't know anybody who tunes carbs anymore.
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  #38  
Old 01-27-2012, 02:41 AM
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mattmopar440 mattmopar440 is offline
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Step 1 go out to your driveway put Jeep in Neutral
Step 2 try to push it
Step 3 realize there is no way in it will ever get "Good" mileage
Step 4 buy a little eco box for your DD
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  #39  
Old 01-27-2012, 01:03 PM
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derf derf is offline
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Quote:
Originally Posted by mattmopar440
Step 1 go out to your driveway put Jeep in Neutral
Step 2 try to push it
Step 3 realize there is no way in it will ever get "Good" mileage
Step 4 buy a little eco box for your DD

That might backfire if your Jeep is pointing downhill on a sloped driveway....
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  #40  
Old 01-27-2012, 02:20 PM
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svining svining is offline
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Milage in perspective

I am trying for 15-16MPG, that's about optimal for these Waggies with 2.73 gears. Nicely tuned. I'm there and will know better in a few more tanks.

I think I live in the right place for good milage mostly improved secondary highways with 45-50 MPH with little traffic.

When you think of Ford Expeditions/Navigators and some other 5000lb Gorilla SUV's we are really right in the ballpark

The really most recent fuel advances come with the 5-6 (now even 8 speed) speed automatics with OD's and high compression computerized engines. I'm waiting for the first ECO-Tech ford V6 to crash.






Quote:
Originally Posted by derf
That might backfire if your Jeep is pointing downhill on a sloped driveway....
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