So basically, nothing.

[Corts60]

I agree with Malibu...sort of. I've been daily driving a square for about 8 of the last ten years. Non-consecutively. My '78 shorty I have now is a 5.7 diesel with t400, GV overdrive and 3.40's in the rear. Doing 75, I get 23 MPG. If I were to slow down, I would more than likely be around 25-26 MPG. But, even so, it gets old driving a 35 year old truck daily, especially in the winter. So I bought a TDI Jetta that gets 37 in the city and 46 MPG on the highway. Life is good now.
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[Rubble]

My job is different than most on here,probably spend 75% of the time on gravel,dirt roads.Lots of rough lease roads that would kill an IFS truck in no time,I have personally saw this with some co workers with their trucks.My solid axle might ride rougher,but it will survive a lot longer.I need a truck for my job,3/4T minimum because of the tools and stuff we pack in them in the winter,50 gallon methanol tank for example.I drive these old truck cause I want to,not cause I have to!! Love the simplicity and durability of them.A new truck doesn't have that,besides once that computer controlled truck is over 10 years old,it's headed for the landfill& my trucks will still be running...
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[cedens]

my 06 half ton sierra is paid for, 100k miles, I figure i can run it till it falls apart, make it a farm truck and go buy a new one.

but yea those bumpy dirt roads are hell on these newer plastic trucks, i almost would consider a ford raptor for some of the oil lease roads i've been on, but you know what my 2wd sierra with traction control has gotten me in and out of a lot of messes.

[Hazieview]

The Fast EZ EFI is suppose to be able to directly replace the carb. People claim to get more mpg and more power.

$2,100 is expensive but since I just rebuilt my engine this would be the most cost effective choice for me. Cheaper than an LS swap for sure.

http://m.summitracing.com/parts/fst-...FVIV7AodTG0Ang
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[tucsonjwt]

20/23 is about what I got on my 2000 V6 Silverado, so I think Keith's experience is completely credible.

I've had a couple Hondas and like the gas mileage, until you need major repairs. You have to get genuine Honda parts because the aftermarket parts always seem to be junk, and those Honda parts are pricey. I'll give up some gas mileage with an old beater Cavalier, but the parts are readily available in the junk yards and genuine GM (relabeled Chinese)new parts are now no more than aftermarket parts (mostly.) Plus, I don't drive either vehicle more than 3K per year.

[StarDust]

well atleast yall not getting 5-6 miles a gallon like me :/ average measured only three times
i drive mine daily from friends house to galveston or gym ect

[Tx79chevy]

I would rather drive my 87 than pay a $300-$400 note on a car that gets 30-35mpg. My square doesn't use $300-$400 in gas a month..
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[meatwagon83]

Originally Posted by Tx79chevy

I would rather drive my 87 than pay a $300-$400 note on a car that gets 30-35mpg. My square doesn't use $300-$400 in gas a month..
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plus gas, plus insurance!!

[dieseldawg142]

Originally Posted by StarDust

well atleast yall not getting 5-6 miles a gallon like me :/ average measured only three times
i drive mine daily from friends house to galveston or gym ect

thats what i get going downhill

[74project]

79 k10. 18 mpg all day long. 80 to 100 on the freeway with a half pedal, I call it the tundra killer...2nd year driving the 5.3l 4l60e out of a wrecked avalanche. Pulling the motor out next summer and into a shot bed crew cab...
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[MalibuSSwagon]

I drive around 15k miles a year, so it's worth it. At 30 MPG average, driving my truck would double my fuel expense. I work in an office so I'm not carrying tools down logging roads every day.

The expenses are cheap, $600 a year for insurance on both Honda and C10, registration $120 a year for the Honda, safety fees $35.

[LEEVON]

The '87 TBI I just sold did 17 mpg over several tank with more highway than city. All city was 14.5-15. This was after I simply replaced the thermostat, prior to that it was 12.5 no matter what.

[Skunksmash]

Originally Posted by slammed427

I plan on a TBI swap and a 5 speed. That should net me near 20 on the freeway. And its paid for, no truck payment can help offset the fuel mileage lost to a new truck.
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Any reason you're not doing an LS? Just curious I guess.

Originally Posted by Corts60

I agree with Malibu...sort of. I've been daily driving a square for about 8 of the last ten years. Non-consecutively. My '78 shorty I have now is a 5.7 diesel with t400, GV overdrive and 3.40's in the rear. Doing 75, I get 23 MPG. If I were to slow down, I would more than likely be around 25-26 MPG. But, even so, it gets old driving a 35 year old truck daily, especially in the winter. So I bought a TDI Jetta that gets 37 in the city and 46 MPG on the highway. Life is good now.
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That's why I drive the wife's Toyota Yaris sedan most of the time. Verified Toyota's claims of 34Mpg city with the AC on. Bout 36 highway. Great car, I love it. But it will always be a little gutless 4 banger squeak toy. Its fun driving the old truck.

Originally Posted by LEEVON

The '87 TBI I just sold did 17 mpg over several tank with more highway than city. All city was 14.5-15. This was after I simply replaced the thermostat, prior to that it was 12.5 no matter what.

That's just weird.

[cedens]

my 82 is what $20 a month for insurance, my commercial policy on the 06 $400 a month (that includes business liability, auto and umbrella) but i can wreck into two classic shelby mustangs and be covered by that policy with a lot to spare.

[Rufton]

Originally Posted by cedens

my 82 is what $20 a month for insurance, my commercial policy on the 06 $400 a month (that includes business liability, auto and umbrella) but i can wreck into two classic shelby mustangs and be covered by that policy with a lot to spare.

Hope you can manage to swerve into two classic toyotas instead

[Skunksmash]

Maybe I asked the wrong question. Maybe its possible to go after the root of the problem instead. What makes my truck get so much less than it used to? I've talked to people who owned them new, and seen the paperwork from GM on the gas mileage. Its well known that it was 17 city, 21-22 highway. I've probably lost 5 mpg.

So what causes it? Age. But what parts have aged? What is directly responsible for the loss in fuel efficiency? You can't really generalize and say "Well its just the whole motor." Cause its not. Its certain part/s that are wore or need refurb'd in some way. I mean I'm just wondering. Do the pistons somehow age? Is it the intake manifold? I'd really like to know the root of the problem. If I knew that, perhaps there would be a way to solve the problem.

Please bear in mind I've done ALL the regular stuff. Plugs, wires, O2 sensor, cap, rotor, air filter, fuel filter, and on, and on and on. Done so much stuff its halfway to being a new truck. So its the old stuff that doesn't get replaced to often.

[MalibuSSwagon]

Well, it is the motor. Every time you run the truck the cylinder walls and rings wear, causing the rings to lose tension, which results in blowby and loss of efficiency. So, the solution would be to rebuild the engine in order to restore the lost fuel mileage.

[Rufton]

May or may not be motor.
I've been surprised how little power and mpg improved post oil drinker engine rebuild.
If it burns lots of oil the O2 sensors can foul and impact mpg.
If it doesn't burn much oil, an after market O2 gauge will always give you AFR heads up which is a critical mpg factor.

[1Cobra427]

After driving bottomless fuel pit of a 454, mine can only, and in the foreseeable future, be a weekend toy. Drive 60miles round trip five days a week so I got myself a VW diesel that gets 45-50mpg and weekends the VW stays in garage. Mon-Fri the square gets garage time. That schedule also releases me to work on the '77 w/o fear of not finishing in time for Monday. If I don't get to something or it takes too long, no sweat. Hats off to the daily drivers I say!

[donut]

You've prob. lost 5 mpg, based on what? EPA gas mileage estimates were VERY generous. What others got can also be a little biased. If it's what you used to get versus now, then somethings wrong that you haven't touched on yet.

couple little stories. 3500hd company rackbody, turbo-diesel. I drove the truck, the best I could get, 17mpg. Former truck driver used the truck, he could knock down 22. That was all driving habits.

Had a couple 4 cylinder, 5 speed, mini trucks (Ford and Chevy) 15-17 mpg.
V-6, 4wd Explorer, 24mpg
1987 Camaro, IROC-Z (wife's car) 305, tpi 27mpg.

EPA (and conventional wisdom) says that the 4 bangers should have gotten better mileage. Driving habits and terrain played into this. SUV and Camaro were barely working to maintain speed. On the highway, there were enough hills that the little trucks had to be downshifted not to lug them down.

Another often overlooked item, the timing chain. Over time they do stretch, May be nothing wrong with it (kinda like an under-inflated tire) but the stretch does contribute to timing enough that if I'm deep in. (changing balancer, pulling radiator, etc.) I'll change it. I changed a badly stretched chain on a 351 Ford, and picked up 3 mpg.

You've got to look at the whole package. The terrain your driving on, are your windows up or down, tire size and inflation, weight in the bed, do you roll into the throttle or mash and brake...

[Skunksmash]

Originally Posted by MalibuSSwagon

Well, it is the motor. Every time you run the truck the cylinder walls and rings wear, causing the rings to lose tension, which results in blowby and loss of efficiency. So, the solution would be to rebuild the engine in order to restore the lost fuel mileage.

But would that really help? I've talked to so many people who say what I quoted below:

Originally Posted by Rufton

I've been surprised how little power and mpg improved post oil drinker engine rebuild.

This. Talked to a lot of people about their rebuilds. Many were expecting things to improve, and nothing really did.

Originally Posted by Rufton

If it burns lots of oil the O2 sensors can foul and impact mpg.
If it doesn't burn much oil, an after market O2 gauge will always give you AFR heads up which is a critical mpg factor.

Needs about 1 quart by the time its due for an oil change. Not leaking, so its going out the tailpipe. I never even add any cause by that time, oil change.

Originally Posted by donut

You've prob. lost 5 mpg, based on what?

My gas pump math and talking to people who owned them new and even some who still own them and get much better mileage.

Originally Posted by donut

EPA gas mileage estimates were VERY generous. What others got can also be a little biased. If it's what you used to get versus now, then somethings wrong that you haven't touched on yet.

That's the opposite of now, where they're more conservative. Did they change since '87? The gub'ment gets more money out of everybody, the worse they can say a car gets. So now they rate them low. For example, on the official fueleconomy.gov site, they say my '09 Yaris Sedan gets 29 city. There have been times when I've gotten 6 more MPG than that with the AC on, city driving. My driving habits aren't any different in that car then they are in my truck. I am not a teenager, nor do I have any illusions that either of those vehicles was ever built with speed in mind. So I drive like a granny in an attempt to save fuel.

The odd thing is, in the Chevy it doesn't seem to matter. I can drive for gas mileage, or go into getup and go mode, and both yield the same result. 14.1 MPG. The most I've ever been able to squeeze out was 14.6, and that was following every rule in the "drive for MPG" book, to the letter. That's with nothing in the bed, OEM tire sizes on, fully inflated. I'm a stickler about my tire pressure.

Originally Posted by donut

Another often overlooked item, the timing chain. Over time they do stretch, May be nothing wrong with it (kinda like an under-inflated tire) but the stretch does contribute to timing enough that if I'm deep in. (changing balancer, pulling radiator, etc.) I'll change it. I changed a badly stretched chain on a 351 Ford, and picked up 3 mpg.

I've often wondered about the timing chain on a lot of the cars I've worked on. You just don't ever want to get down into it unless you have to. It sure would suck to dig all the way in there to check it, only to find out that it was fine.

[Rufton]

You can quickly check TC slop.
Turn crank CCW then CW by hand while watching rotor.
I recently built engine w/ huge oil consumption and huge TC stretch and mpg is only slightly better so far. Only have one decent data point due to mostly city driving.

[donut]

On the Ford, if I got into the gas, it would start backfiring badly.
Got into the chain and it had enough slop to pull it off the gears without pulling either gear.

My '03 Trailblazer gets about 16mpg. That's the good vehicle. Straight 6, computer controlled, decent power. But it's 4wd and the long wheelbase (ac works though..). Others report to get low 20's with the same setup. After tracking mileage for 60kmi., I've decided that's normal for me. So like with any mileage thread, YMMV.

What you mentioned about the windows is true, windows open in the TB and mileage will drop to high 14-15. So it's not surprising your wife's car is so much better.

[Skunksmash]

Originally Posted by Rufton

You can quickly check TC slop.
Turn crank CCW then CW by hand while watching rotor.
I recently built engine w/ huge oil consumption and huge TC stretch and mpg is only slightly better so far. Only have one decent data point due to mostly city driving.

I know very little about this subject. Is there supposed to be zero "slop"? On any vehicle, I mean. Basically, when you move the crank, even a little, the rotor is supposed to start moving as well. Or with some cars, might there be a slight delay? How much slack in the chain is acceptable?

Originally Posted by donut

What you mentioned about the windows is true, windows open in the TB and mileage will drop to high 14-15. So it's not surprising your wife's car is so much better.

I do drive with the windows down, but still it hasn't changed much. I used to drive with them up back when I still had AC. Gotta get that fixed.

[Rufton]

By eye, a new chain will appear to have almost no slop (wild guess = less than 5 degrees).
A stretched chain will have obvious slop of a few degrees (wild guess = more than 10 degrees).
If engine is well maintained, it may last till chain stretches so much that it jumps teeth and causes engine to run bad.