Mpg to expect on an '82 C20 3+3, 350?

[JACK34]

Who really knows what's in the tanks at the gas stations. I just have always ran either 91 or 93 octane fuel in everything not ethanol. But I didn't get a gas guzzling truck for the fuel mileage so I don't care. Like I said before if you are that worried about gas mileage get a Prius. No offense to the Prius owners.

 

[Rusty Nail]

Well, higher octane gas is less prone to detonation ... Lemme keep thinkin about it. Thanks for the update.
Obviously the thought is towards ignition advance but I'm thinking there is something else at play.
Im doin something different right now I'll get back atcha.

 

[Rusty Nail]

The knock sensor can pull timing.. but what else..?

I gotta log out or I'll never get anything else done.
Coolant temp too high or Perceived temp. (by the computer) That could also pull timing.... What else?

What is your operating elevation above sea level?

Oh lol the OP split. Very clever Mr. Tricky but you'll have to get up earlier than that!

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[Buck69]

Damn. These numbers sound horrible.
Sure glad our gallons are bigger!

 

[HotWheelsBurban]

Damn. These numbers sound horrible.
Sure glad our gallons are bigger!

Yeah but y'all still buy it by the liter, right? Or is that just in Europe?

 

[Camar068]

I swear I wish I had some peoples issues/problems/delima's lol. If you put a 4x4 square burb or 3+3 side by side, I don't know which one I would take.

 

[Octane]

8 mpg. My 77k10 350 auto w/ 373's and a fulltime np203 gets max 12.

 

[CountKrunk]

I calculated mine and got 16, then i realized that the odo isnt accurate. The gas gauge is busted. I use an app to track mileage and speed now. That said, i haven't filled it up in a while. Its not a daily, so most trips are <5 miles.

But, i smile every time i drive it, so who cares!

 

[T-roy K10]

Not the same truck, but my 85 k10 got 16mpg on a 130 mile trip running r4 a/c the whole trip. It a shorted with a carb’d 97 vortec 350. 33s and 4” lift.
Oh, and 3.73 gears and th350.

 

[Ricko1966]

Okay you can't compare a tbi truck with O.D. for fuel milage. The swirly heads are good for some mpg the O.D. transmission is good for some more mpg and the TBI is good for more still. My 350 700r4 TBI burb would knock down 17mpg all day long.

 

[SirRobyn0]

I don't know if I'll be very helpful but this is what I have in the mileage department.

First of I think it sucks when someone is asking about miles per gallon and someone posts a response that it doesn't matter.....

Gas mileage! My 1984 C20 305 700R4 3.73 truck. I get right around 12 going back and forth to work, which is a mix of country roads and city traffic. On the highway if I'm driving I-5 where there are hills but not mountain passes I routinely get just below 16, generally it'll be close to 16, like 15.8 or 9 typically. If I cruise at 60 in the slow lane I can get over 16, but that's a pain in the butt for me, I'd rather run at the flow of traffic which generally is 70 - 80, but the MPG drops off in a hurry over 75 or so. Running 80 on trip deduct 1MPG. The worst mileage I get with her is when I do I-82 (three ridges to go over) and I-90 Snoqualmie pass with a loaded trailer that's an 8MPG affair. So yea it can vary that much. And sometimes I think about a 454 or even a 350. When my little 305 dies the plan is to put a 350 in it's place, but I know that'll lower my overall mileage a little bit at the benefit of better power and loosing the idiosyncrasies of the 305. If I had a 454 truck it could not be a daily driver for me. With the 305 I can DD her. So I might crest Manastash ridge at 35MPH with the trailer loaded, but the trade off is 16MPG on the highway when running empty. But I'm known guys with 350's in these trucks and 4.10's and no OD and they never made it much past 10MPG, one friend use to have a 350 C30 in a 72 (so not really a square), his truck was set up for a camper and had 4.56's with the TH400 and he generally got 8 - 9MPG.

I guess my point is the combination of engine, transmission and rear end gear ratio can make a large difference in fuel economy.

 

[Rusty Nail]

It doesn't matter ??

Meh I already said single digits, i'm stickin with that.

 

[GTX63]

If your truck is a daily driver that doesn't require polishing, pampering and high end maintenance, the gas mileage isn't such a bad thing. Not when compared to say a 10 year old 30k truck that needs a scan tool and modules, sensors and certified techs to make repairs, for 2 more mpgs.
My 74 C10 350 2bbl turbo 350 3.08 gear gets 10/12 mpg.
My 80 GMC K15 350 Qjet 350 turbo 3.73 gets 12/14mpg.
My 85 Chevy K10 350 Edelbrock 4 bbl Turbo 350 2.73 is 11/15.
Tuning, tires, gearing, weight.

 

[SirRobyn0]

If your truck is a daily driver that doesn't require polishing, pampering and high end maintenance, the gas mileage isn't such a bad thing. Not when compared to say a 10 year old 30k truck that needs a scan tool and modules, sensors and certified techs to make repairs, for 2 more mpgs.
My 74 C10 350 2bbl turbo 350 3.08 gear gets 10/12 mpg.
My 80 GMC K15 350 Qjet 350 turbo 3.73 gets 12/14mpg.
My 85 Chevy K10 350 Edelbrock 4 bbl Turbo 350 2.73 is 11/15.
Tuning, tires, gearing, weight.

I completely agree with this:

compared to say a 10 year old 30k truck that needs a scan tool and modules, sensors and certified techs to make repairs, for 2 more mpgs.

And no car payment for the square, cheaper tabs, cheaper insurance, lower repair cost...

 

[GTX63]

My late model 2500 Silverado gets 11mpg unloaded. It is laden with whistles, bells and ticklies. If it quits while I am on the road, well, I am stuck and the repair isn't going to be cheap.
If my Squarebody dies, 90% of the needed parts will be stored in the glovebox or behind the seat, ie coil, ignition module, fuel filter, fuel pump. Any less fuel mileage is offset by depreciation and repair costs for the newer truck.