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Discussion Starter · #1 ·
Planning on taking the 289/c4 combo around the country with my friends.

I get about 13mpg in town. I'd like to get about 18-20mpg highway if that's possible. I know swapping the 2bbl out for an edelbrock 4bbl would help tremendously at cruising speeds, and would enable me to have more fun accelerating.

Also, I'd like an overdrive tranny and a lock-up differential, I'm sure that would give me another 2 or 3 mpg highway. An C4 to AOD swap out is pretty straight forward, right?

Any other cheap and inexpensive ideas to help me maximize my fuel economy? Any comments about the carb and tranny? I'd like a stick, but a 5-speed with overdrive is too much a pain in the @$$.

Thanks
-MAtt
 

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You could install a higher gear in the rear end. Not sure what you have but find something in the 2.75 range.
 

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my understanding is if you want to maxiumize fuel economy on these cars, is the smaller the carb the better since you will be squirting less gas down the intake. a larger carb is just allowing you to attain higher rpms.

go light on the accelerator, so you don't keep dumping the accelerator pump of fuel also.

changing to a taller rear gear, like 2.75

and driving with a vacuum gauge hooked up, you want to drive at speed with the maximum vacuum reading, making the most efficient use of your fuel atomization.


traffic, there isn't much you can do about that as just sitting and idling is going to suck gallons down the drain, invest in a GPS with Live Traffic coverage. if you can plan ahead and take a detour it could save you a lot of money in fuel also, and get you to your destination faster.
 

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Also don't forget proper tire inflation, alignment, even a clutch fan.
 

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Stretch your stops to the max to avoid stopping and starting. Max out your tire pressures, use a 10W-30 full synthetic or Motorcraft Synthetic Blend, and install a cruise control unit.
 

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Overdrive! That will go a long way, especially on the highway. I just added a Gear Vendors bolt-on overdrive unit and my fuel mileage has greatly encreased! Now I can still run my 3:50 gearset and still drive 65 on the highway and get decent mileage. An AOD would be a great upgrade for you.
 

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My 289 C-4 2-V came with a 2.73 out of the factory. At 70, the tach still shows about 3000. Seem to get 16-17 no matter where you drive it.
 

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Jim Carrol said:
my understanding is if you want to maxiumize fuel economy on these cars, is the smaller the carb the better since you will be squirting less gas down the intake. a larger carb is just allowing you to attain higher rpms.

Essentially this is true. However, a four barrel can be a lot better than a two barrel because most of the time the secondaries are not open - so you are down to a smaller two-barrel. The secret is getting the right four-barrel, i.e. not a huge one!

Anyone please correct me if I am wrong.
 

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Discussion Starter · #9 ·
Jim Carrol said:
my understanding is if you want to maxiumize fuel economy on these cars, is the smaller the carb the better since you will be squirting less gas down the intake. a larger carb is just allowing you to attain higher rpms.

go light on the accelerator, so you don't keep dumping the accelerator pump of fuel also.
My understanding was that 4 barrel carbuerators guzzle more gas during accleration and thus go faster but burn more fuel in town, but that they were actually far superior to 2bbl carbs fuel-economy wise if you drove them easy and at low rpms. So I assumed that even if i let my testosterone get a hold of me every now and then, when crusing at low rpms on the highway, the secondaries would shut off, and i'd get better mileage than a 2bbl.

Am I wrong? I really could be.

I'm still learning this
-Matt
 

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Spark upgrades should help. Long tube headers may as well.

Lastly, nothing will help you more than a good tune (especially after the ignition upgrades).
 

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Swapping to a 2bbl wont necessarily give better mileage. The primaries on a 500/600 cfm Edelbrock, are smaller in volume than a stock 2bbl.
Not only keep your foot out of it, also easy pressure on the pedal. Maintain not a steady RPM or MPH, rather a consistant pressure on the on the accellerator.

Get an OD tranny
 

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An AOD swap is a great upgrade, but it's not as simple as just bolting it in place of the C4. The conversion parts are available in the aftermarket because of the popularity of the swap, so it can be done with little or no custom fabrication. A crossmember will be needed to fit the different mount location. A throttle valve (TV) cable is used to control shifting instead of a vacuum modulator. There are linkage adapters you can buy that attach the TV cable to a carb. Lokar makes a good TV cable that is simple to adapt to non-stock applications. Also, the stock C4 shifter won't work as is. You need either a cable operated shifter made for the AOD or a linkage rod from the aftermarket that adapts the C4 shifter to work on the AOD. Your driveshaft should work without any mods but you'll need the correct AOD yoke. Given the cost and work involved in the swap I would hesitate to take on the project just for a road trip. I doubt the cost of the gas saved by the AOD on this one trip would equal the cost of the conversion. If it's something you've been wanting to do anyway then this is a good time to do it, but if you just want to do for the sake of gas money and you're otherwise satisfied with the way the car drives I woud just focus on more traditional methods of improving mpg, i.e. make sure tires are properly inflated, spark plugs and wires are in good shape, etc. Swapping to a 4 barrel carb is also a nice upgrade and can yield a minor improvement in mpg IF you drive sensably. Driving slower will net the biggest mpg gain. My 1st 'stang was a '67 289 2V with a C4 and 2.87 rear gear which got 16-17 mpg. If you install a pertronix or similar type ignition, make all the other mpg improving adjustments and keep the speed at a steady 60-65 you should be able to get close to 20 on the highway even without an AOD.
 

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Swapping to an overdrive trans will not necessarily get you better mileage either..If depends on your rear end ratio...If you have some highway gears in the rear end already cruising in overdrive may make the engine work much harder trying to push the car..
 

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:lol: Yeah an overdrive trans with 2.73 gears and some really tall tires might get you at a 1500rpm cruising speed. There is an RPM sweet spot for max fuel economy, below and above it the fuel economy drops off. I think around 2000-2200 is a typical sweet spot for fuel economy, but this all depends on your motor and components.
 

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I think an AOD will get you better miliage. But depending on how much you drive, it migh not be worth it. I'm considering the same swap and did these calculations yesterday:

I figure it would cost me $1000 to do the swap as I already have a good used running AOD. It may cost you more or less, but don't forget the driveshaft.

My '65 289/c4/3:00 can get 20mpg baby driving on the freeway.

I figured AOD would give me 2 MPG more.

@$4/gal gas, $1000 to swap OD tranny, 20mpg vs 22 mpg, means every 10gals, you save 1gal, every 220 miles, save $4. $1000/4 = 250x220=55,000 miles

I'd have to drive 55,000 miles to make it up in this case. I probably wont do the swap. But if you had 4:11s, the MPG increase would probably be dramatic.

I'm not a math major, so check my numbers - they might be off.
 

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Classic Mustang V8 automatic on a road trip with friends.......
Great place to start looking for economy!
1. Tune it!
Don't have your engine working against itself.
2. Drive right!
Keep your foot out! I find this to be the most
difficult thing to do when driving a classic Mustang. I have never been capable for more that 15 minutes.
3. Minor mechanicals!
Brakes dragging a little? engine accessories up to par? Trunk full of heavy stuff? Full tire inflation?
4. Major mechanicals!
Lots of good stuff already posted.
I am a 5 speed fan myself and have found that
you can get a triple benefit with the proper rear gears. Acceleration, economy, fun!!

I use most for my pizza delivery car (32-34 in town) and it seems to work.
Skinny tires, no trash, tuned obsessively!

Bruce
 

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Is this your first long road trip with the Mustang? If so, save money now for on the road repairs. Basic stuff - how many miles are on the engine, trans, etc. Any mechnical work done recently - timing chain, trans filter replacement, new diff fluid, radiator flush, etc? I'd hate for you to be stranded far from home with a dead engine or slipping transmission. After all, you are driving a 40+ year old car.

A long road trip might be more economical with a newer 4 cylinder car. Not as fun, but it may be cheaper in the long run.
 
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