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My vintage wagon, still with 22,000 original miles sees summer duty as a short distance commuter and pleasure ride. typ .1000- 1500 miles added/year.

seems to average about 20mpg on a tank.
OK. short trips are not great for mileage, and the 3sp auto does no further favors, but i would expect somewhat better fuel economy.
are there any screws to adjust that might result in improved fuel efficiency?
the car has been bulletproof reliable on the engine front. always starts. had to replace fuel pump in tank some years back and replacement plug wires to solve a cracked one for intermittent grounding of the HV thru old wire insulation. that's it. has seen no salt. no system leaks.

thanks
 

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My car is a '90 cfi, originally came with the 3spd automatic. Mine too was in the low 20's. Honestly, the single best thing I've done for my economy was swapping the auto for a 5 speed. That alone got me close to 30 mpg. Since then, I replaced my broken front bumper with one from a Topaz (more aero, less holes)- that got me to 30 mpg. I advanced my ignition timing a little, increased my fuel pressure a little, lowered my idle speed a little, added a rear spoiler... I just got 36 mpg on a recent road trip. I'm going to be trying some more advanced things, like under car aero, and a longer ratio transmission- I drive over 50 miles a day, half of which are on the Turnpike at 70 mph+. My goal is 40 mpg.
If a manual swap is not an option, just make sure the engine is healthy. Other things to try- use synthetic oil, do a good tune-up, new filters, change out the O2 sensor, etc. Parts for our cars are stupid cheap on rockauto.com.
Make sure the alignment is good, overinflate the tires (I run about 40psi), make sure the brakes aren't hanging up.
Driving habits also make a difference, too.
 

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1988 EXP 2.0l H.O on bike carbs.
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Shorty hit the nail on the head. Also make sure your aliment is good, even being off by a little can kill MPG. Driveing at 55 helps a lot too.
But keep in mind that old MPG stats do not apply today with all the ethanol in gas today. I get about 8% more MPG in my 2019 fiesta with ethanol free gas and I'm sure its worse on a escort.
 

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There's a lot to unpack here, but to get the best you can follow every tip you can mentioned before me and these I recommend:

The 3-speed is going to be your #1 fuel killer, 3rd gear is only about 1:1 so you technically don't have an overdrive, this is going to kill your mileage any time you're over 45-55mph. The manual 4 & 5 speeds have a top gear overdrive that raise your mileage-drop-off point to about 65-75mph.
If you can't manual swap we understand, it's a simple undertaking but requires an entire parts car making it an exclusive process to those with time & space. One alternative is fitting taller tires, if you can add 1/2" or even 1" to your total tire height this will make a big difference for little cost, your speedometer will be off but now you'll have taller gearing to improve your mileage at 55-65mph but can have a negative effect on your in-town mileage if your engine doesn't have much low-end power/torque. Remember to recalculate your mileage for the inaccurate speedometer+odometer readings, if your car does 60mph when the gauge reads 55mph you're getting 1.11 times as many miles per tank than it shows for instance - my 82 4-speed is like this with my 195-60r15 tires.

Weight & engine power-robbers are your next concern, if you're able to remove all emissions provisions (catalytic converter, smog pump if present, EGR) you'll free up say 5hp but more importantly you'll be ditching 10-30lbs from the front of the car and that's a big deal when in these cars every 50lbs makes a difference in how they drive. Sadly you still have a rather heavy car being a wagon so your MPG will always be limited, mid 30s is probably the best you'll ever achieve.

Engine tuning is the next concern, like mentioned above making sure it's all up to date with strong (misfire-free & well timed) ignition, fresh synthetic oil (going from Pennzoil to Mobil-1 synthetic can increase your economy 1-5mpg for instance), insuring the cooling system is strong, using a fresh air filter, etc make sure it's running the best it can. After that you can do a few things to help even more, make sure your idle speed is as close to 750rpm as possible, and there are probably other simple techniques for the CFI but they're outside my expertise.

Also be sure your tires are fully or a little over inflated, running 5-10psi low in any one tire drops my 82 from 37mpg to 32-35mpg. Your setup can be different but I set my tires to 37psi instead of 35psi and there's no consequence because it's not a huge difference, but if I were to go to 45psi then how the car handles, brakes, and wears tires would be very problematic. Making sure alignment and tire balance is correct is equally critical, they won't affect your acceleration MPG as much as they'll affect how far you'll coast and that's the bigger deal. Just having one wheel out of balance enough to make your steering wheel shake can REALLY shorten your coasting difference, I found this out after I rebalanced my right steer tire that lost a weight this spring, WHAT A DIFFERENCE!!

Before more in-depth engine mods is simply how you drive:
Don't let the car run too long while warming up, the second idle drops down to where it normally is when warm you're ready to drive (the temp needle will usually just start to move at this point), waiting any longer just burns more fuel. Same with when you reach your destination, don't let it run for minutes after, as soon as you're stopped 5-10 seconds of run time is all you need before you pull the key out.
Peak torque is around 3000-3500rpm so don't go past that when accelerating. On the topic of accelerating just take your time, modern cars with 6-speed autos are going to naturally out-walk you from a stop to 55mph, just let it happen because if you try keeping up it will cost you even more. For me this is the difference between 37mpg & 44mpg in my 82 4-speed.
Let it coast as much as you can, braking at the last second vs timing when to let off and coast to your stop to minimize braking is the difference between 32mpg & 37mpg.
Take turns quicker vs slower, if you can coast through a turn instead of braking then reapplying throttle you'll save a lot of fuel. But obviously don't get reckless, taking a turn faster than you or your car is comfortable with will always end poorly, just if you can comfortably & safely take a turn at 35 instead of 20 then do it.
When encountering hills try to get above the speed you want to go up it before you reach it, I climb a nasty hill to work every day that normally knocks my 55-60mph down to 35-40mph when I reach the top, if I can get up to 65mph before I reach the hill I can still be at 45-50mph when I reach the top. Bogging down to 35mph up it is hard on the car in top gear so you have to down shift which is hard on your fuel economy so try to pre-plan any hills.
Also keep windows up above 35mph and in general try to keep your A/C off if equipped. When the wind is just right rolling up the windows in my EXP makes it faster without me moving the throttle if you can believe it.
Lastly like I said, every 50lbs makes a difference in these so make sure you're not running around with extra stuff in your car, 1 adult passenger still yields acceptable MPG but a passenger with a 25lb backpack, 60lbs of groceries, 25lbs in your emergency tools & fluids, and a coat & umbrella you left behind last it rained combined will KILL your economy.

As far as engine mods go there's a lot to help with power AND economy, just know that there's a number of things that aren't going to be a cost-effective improvement unless your quest for power exceeds your quest to save money on gas.
Headers will help but make the exhaust noticeably louder by your feet and you have to change out the majority of your exhaust so you really have to weigh the cost of parts vs the minor fuel benefit, this is one of those things that's done with power in mind first.
Roller rockers are similar, they'll help power some and economy a little bit but the cost is so much higher than what you'll get back in fuel savings it's also not worth it to the normal joe.
Now what is cost effective is porting the head, at the cost of only a $15 headgasket or $20-$35 gasket set and some sand rolls for a dremel tool you can really open the taps on your power AND improve fuel economy some. Guarantee you'll get your money back in fuel savings after say 4 tanks - assuming you can keep your foot under control with the new power haha If you want to splurge a tad more, $40 of machining will shave your head some to raise compression which increases power and possibly economy some.
Another cost effective thing you can experiment with is a $15 1.6 cam sprocket, with this installed you change your can timing + or - 4.8 degrees. This will move your power curve closer or farther to redline (retard raises the curve while advance lowers the curve) which will help your in-town or highway economy too. This is definitely recommended if the head has been shaved. Just remember if you change sprockets you need to re-time your ignition! haha
 

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Headers will help but make the exhaust noticeably louder by your feet and you have to change out the majority of your exhaust so you really have to weigh the cost of parts vs the minor fuel benefit, this is one of those things that's done with power in mind first.
I put a GT header on my CFI 88 and all I had to do was remove the stock cat/downpide and block off the EGR. Granted that is not always an option.
 

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If you can do the transmission swap finding a 4 speed out of a Pony is probably the best bang for your buck. I drove an '88 Pony until it had 518K miles on it and very seldom did the mileage drop below 40 MPG. When it did I was looking for the problem. I was driving it to work at one time that was a 65 mile drive each way and included about 45 miles of interstate each way where I usually had the speedometer hand buried to what I suspect was 90-100 MPH and still was able to break 40 MPG consistently. Once on a longer trip I tried to stay as close to 55 MPH as I could and managed to get 50 MPG out of it. I've still got the '88 sitting in my yard, wish that transmission was in my '94 LX.
 
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