MPG. I need some more Brains to help me out.

[cowstick]

MPG is about 10-12 if im lucky. any Suggestions what i could do to raise it up some.

[BLE 'BURBAN]

change out the rear end gears for a lower number i.e = from 3:73's to 3:08's or 2:92 or a gear vendors overdrive unit so you'll have the best of both worlds.
Pete Santini in California has/had a crew cab that he installed 2 gearvendors overdrive units into behind the factory TH700R4 trans that was in it. They had a write up on it in truckin' magazine about 10-12 years ago.

[piecesparts]

Here we go:

What are you running for engine, tranny, gears, tire size, and RPMs? Do you drive the higway or the city the most? Do you haul anything more than your own self? You have to look at this as a quest for that perfect driving goal. Get the RPMs at the right level and the power and MPG are right behind it. What do you have your engine timing set at? What carb do you have? What do you have for an exhaust and air intake? Are you still running the factory fan that is belt driven? What do you inflate your tires to? Is the truck sitting hig off of the ground or is it lowered?

As you can see, there are numerous things that you can change and gain power and economy.

[LOHRTBT]

Easy...put a 6 cyl in it lol

[Pyrotechnic]

First of all, what are we working with here ?

Engine Size ?
Engine - Stock or modified ?
Transmission ?
Rear end gear ratio ?
Tire height ?

Truck?
2WD or 4x4 ?
1/2, 3/4, or 1 ton ?
Regular or Crew cab ?
Short or long bed ?

What conditions do you primarily drive the truck ? City, highway, or do you expect to get good gas mileage with both ?

[EN*PN78]

Originally Posted by LOHRTBT

Easy...put a 6 cyl in it lol

L6 it for certain.

[cowstick]

No tach in it so i cant tell. I got all the replacements for the fuel filter air filter plugs wires Ill let ya know what happens. If it helps Truck shifts at about 35mph and again at around 55mph o probably running about 5000 at shift point but i cant be sure.

[dieselarmy13]

Put an egg under your accelorator

[babyJay]

Replace the O2 sensor...That's one of the things my V30 just got. Mine was crusted up with green scale of some sort. I read a chart on the counter @ O'Rielly that stated how much gas a year if could save, and it was far more than the comparison for spark plugs.

[PhilaTruck]

Originally Posted by dieselarmy13

Put an egg under your accelorator

Sounds like a joke, but it's true; driving easy on the gas pedal will make a big big difference. Oh, that is after you've done an extensive tune-up. And like GChemist said, make sure your carb is functioning properly. BTW, I doubt you're shifting at 5K unless you've got it mashed, which would explain the mileage.

I used to get low 20s highway with my 2wd 305:2.73- driving on eggs.
Let it ease up to 50-55. Don't go any faster than that, your truck gets "heavier" by pushing more air and your mileage goes down.

I could also get 12 mpg with that set-up.

[cowstick]

I guessi did leave that vauge sorry. ok here it goes.

Engine Size ? 305 V8
Engine - Stock or modified ? sadly just stock for now
Transmission ? auto overdrive and what the factory put in
Rear end gear ratio ? no idea but i know its stock
Tire height ? 235/75/15

Truck? 1986 GMC Sierra K15
2WD or 4x4 ? 4x4
1/2, 3/4, or 1 ton ? 1/2
Regular or Crew cab ? Regular
Short or long bed ? Long soon to be step side

[gchemist]

Tune the carb.
http://www.centuryperformance.com/

[streetstar]

i don't know -- those trucks got decent mileage when they were new (18-20 mpg)


Maybe you should buy a Kia (or freshen up the plugs, wires, dizzy, and carb)

[cowstick]

Thank you for the info. If it wasnt snowing out (love minnesota) I would be doing that today.

[us111]

hello,i would certainly go with new everything
when weather permits,fuel filter,wires,plugs,air
filter etc and go from there .I'm running a 5.7 carb'd
out of a 99 escalade in a 1976 k-10 short bed stepside
and get around 14mpg on highway,so i certainly think
u could do better than 12mpg in a 305 with a basic tuneup.

[piecesparts]

Do you have a tachometer in the truck? Do you know what RPMs you are running on the highway? This would help to tell us what your rear end ratio is. The fuel mixes for the winter months (in most cold states) is an alcohol mix and whatever precentage the gas has in ethanol is the percentage your fuel economy decreases. BY the way the stations DO NOT have to list if they mix ethanol in their fuel any more---many don't even know. I agree with the others, get a good tuneup and do take al ook at your timing. See if it works better alittle bit advanced. The computer may dork you there, but the more advance the better you can get in mileage. Keep the tires i nflated, look at restrictions in your exhaust and improve there. The removal of the stock engine driven fan was worth a whole Mile Per Gallon on my daily driver.

[Rooster's82]

I want to know more about the o2 sensor. I haven't heard much about that at all.

best way to save gas....walk, HAHAHA just kidding, i don't walk to my mail box. drive slow, I love just cruzing along doing the speed limit or a little less watching everyone blasting by in such a rush to get somewhere they really don't want to be, while i am exactally where i want to be: riding down the block in my truck, thinking life is good.
I took my GF out in it for one of the first times the other night, she refused to ride in it for awhile, it had roaches, anyway she looked at me driving it and could not believe how happy i was. I think she understands a little better why i work on it so much and how much it means to me. (by the way, we are talking about the truck you see to the left...still looks pretty much the same on the outside)

[babyJay]

Originally Posted by Rooster's82

I want to know more about the o2 sensor. I haven't heard much about that at all.

Mine's an '87, it's TBI injected. Not sure if the carbed version of these had one. I know my '79 doesn't. Just headers and duals. They are usually threaded into the exhaust close to the manifold, but on the pipe.

[Rooster's82]

HAHA, i know what an o2 sensor is...i guess that was a stupid question. I wanted to know more about how it saves fuel, but now that i think about it, it determines how much o2 is coming out of the exhaust and adjusts fuel ratios accordingly. So a non-functional one would have quite an impact on MPG. I don't think i have one on my '82.

[babyJay]

yeah.....what you said.

[Rooster's82]

what about an electric fan? they claim more power and more mpg. I read 2-3 more mpg.

Does anyone have any info on them?

[piecesparts]

Originally Posted by Rooster's82

what about an electric fan? they claim more power and more mpg. I read 2-3 more mpg.

Does anyone have any info on them?

I put a dual electric fan setup in my 91 Daily driver, with a 5.7 liter V-8. The fans gained a solid 1 MPG and the engine started and run better, than with the factory clutch fan. the warmup time in the winter is cut in half, and the control of the temperature in heavy traffic is better. That was a geat investment, as far as I can see. You would want to research fans, a little and see what is out there. There are so many different approaches to cooling fans and you would want to get what works the best. I also am running an electric fan set on my 84 GMC SWB. That truck has a 383 stroker motor with a 2400 stall convertor on a 700 R4 tranny. The truck has a set of 3.73 rear end gears and I still get 15 MPG at 70 MPH highway speeds.

The goal is to get your truck to drive in the OPTIMUM power band and not be lugging the motor to either come up to speed or maintain the speed. That is where the right size tire and gear ratio is important. I have mine set up to run at 75 MPH and the engine is turning around 2600 RPM. That is where it gets the best economy on the highway.

[PhilaTruck]

Nice post piecesparts.

Here's a great "how to" from our FAQ regarding electric fans, if you're interested.

FAQ: Electric fan how-to

[Rooster's82]

how much better is a duel fan setup to a single "universal" electric fan that fits in the factory shroud? Will it draw enough air? For example:http://www.jcwhitney.com/autoparts/P...001645/c-10101

[babyJay]

Originally Posted by Rooster's82

how much better is a duel fan setup to a single "universal" electric fan that fits in the factory shroud? Will it draw enough air? For example:http://www.jcwhitney.com/autoparts/P...001645/c-10101

You would need to eliminate the factory shroud. It's not needed.