What kind of fuel mileage do you get?

[Fly By Night]

I drove my truck to Utah last weekend and managed 12mpg over a half tank going 70-80 with some runs faster then that, I was pretty impressed by that.

350
Quadra Jet
Headers/Dual Exhaust
3.73's
4 Speed

What do you get?

[Ed F]

On a 200 mile trip last fall, some interstate at 65-70, some 2 lane at 55-60, and a little around a small town, I got 18.3 mpg. Couldn't believe it, I thought the gas guage was broken until I refilled the tank when I got home. That was my '70 C10, 350, 1977 Olds Quadrajet, headers and 3speed manual. I was going to replace the carb with correct Qudrajet but after that trip I have left it alone. Most of the other highway trips I have taken with that truck, I was towing our 18' Chris Craft and got about 12 mpg which I think is still really good.

[mike16]

68K20 327 4bbl......7-9 mpg with 456 gears

[garyd1961]

I just installed a GM L31-R crate engine in my truck. I have a Holley 750, long tube headers with 2 1/2 inch exhaust out the back, th350 trans with 307 gears in the rear. I've only got a little over 200 miles on it and haven't checked the exact mileage but I'm really impressed with it. I would be surprised if it isn't getting better than 15 mpg.

[givememytoys]

69 C20 with a 292, granny 4 speed and 3.73 gears. I get between 15-17 MPG at 65mph depending on the wind.

[Stocker]

Haven't really checked mine in a very long time..... many years ago I did about a 3700 mile trip and averaged 11.5 mpg iirc. Truck info in sig, 4.10 gears.

[un4gvn!]

69CST396-Bored and stroked to a 440 with 11.1 compression, Houghes 400 Turbo transmission, 3:73 posi, 21 gallon gas tank. Tanked it up going to work which is 35 miles away at mostly 50-60 mph. Came home after a 70 mile round trip. Pulled into the garage and saw there was only an 1/8 of a tank left. To scared to do the math.

[special-K]

12.5 MPG in my '72 in signature. The K/20 Highlander I had got the same. That truck had 400 SBC 4bbl, 4spd, 4.10s, & 315/75. All mixed daily driving

[Alex V.]

'85 C3500, 454/TH400/4.10's, SRW, all stock, curb weight approx. 5,250 lbs.: 12.5 at a consistent 55-65 MPH on the highway, without cruise. 9.5-10.5 when towing 6-10,000 lb.

'67 C10 Suburban, 350 (close to specs of the base Goodwrench crate engine - 76 CC, 1.94 intake heads, .383/.401" cam) with Rochester 4G and iron intake, points distributor, ram's horn manifolds with dual 2" exhaust, all stock otherwise, NP435/3.73's, 30.5x10r15 tires, approx. curb weight 4,600 lbs.: 14 MPG at a steady 60-65 MPH, more like 13.3 with 4 people, a lot of luggage and a Honda 175 motorcycle in the back.

[davepl]

Pretty sure these are 12mpg, maybe 14 for a carefully driven six cylinder. You'll hear hero stories of 20+ mpg one way and so on but nothing we can do can match the efficiency of a modern Silverado, so you have to look at what they get (they're probably heavier though) and sort of set that as a reasonable maximum I think.

[Grumpy old man]

We're dealing with 50 year old trucks with the aerodynamics of a shoe box , Just because you drop a late model drivetrain In it does'nt mean your gonna match any sold today . You really have to consider whether you want to drive a cool truck or count pennies by driving a cool truck ? If you really need to worry about gas mileage park it and buy an old Honda 4 banger to daily drive .

[70STOVEBOLT]

Originally Posted by un4gvn!

69CST396-Bored and stroked to a 440 with 11.1 compression, Houghes 400 Turbo transmission, 3:73 posi, 21 gallon gas tank. Tanked it up going to work which is 35 miles away at mostly 50-60 mph. Came home after a 70 mile round trip. Pulled into the garage and saw there was only an 1/8 of a tank left. To scared to do the math.

I think your gas gauge is wrong. If not, then WOW!

[70STOVEBOLT]

I only have about 500 miles on mine since the big block swap, so I have not really checked it out yet. I got 14-15 with the 250/TH400/3.73 combo. That was mostly back and forth to work-13 mile round trip at 50-60 mph. I am hoping to get at least 11 with the 402. All stock, except mild cam and 750 Eddy carb with 1" spacer.

[Andy4639]

My 71 has factory 4:10 gears along with 6.0 4l80E over drive and it's doing all it can to 16-17 on the open highway.
I compensated that with a 42 gallon tank though! I got right at 600 miles out of one tank back in 2014 on the hot rod power tour without running the AC at all driving on interstate the whole time coming home from Dells Wisconsin. I had some left but I had never driven it that far so I got scared and filled up.I made it home on the one fill up. That's 950 miles I drove straight through that day. I left at 11am that morning and at 3 am next morning I pulled into my garage in Liberty! About 14 hrs total
That was stopping for a friend who blew a distributor cap out to and finding a parts store for him. Fixed it on the side of the interstate! Several bathroom stops to.

[tdangle]

1970 C20, 350 4BBL TH350 4.10 gears 10 mpg doesn't make a different how I drive.

[Blue/72]

I have a 72 with rebuilt (but orignal engine) 350 small block, th350 and 3:73 gears and at 60 I'm getting about 17

[davepl]

Originally Posted by Blue/72

I have a 72 with rebuilt (but orignal engine) 350 small block, th350 and 3:73 gears and at 60 I'm getting about 17

I presume that's highway - I doubt these trucks could come near that in city or mixed driving, at least not when modern trucks are putting in 12 or so City.

[RINC]

69 C-20 350ci/TH400 with Gear Vendors OD, 4:10 rear

Need to log this stuff after the next fill up, and do the math.

Usually put about 12g after 2 weeks of driving to work an running errands.

[GRX]

Another MPG thread if interested:

67-72chevytrucks.com/vboard/showthread.php?t=548916

As for me, I get about 8-10 mpg around town. c10 long bed step side, 250 engine, 1bbl carb. Not stellar mileage, but it runs great and I do get plenty of smiles per gallon.

[Sicklajoie]

69 C/20 with 350ci, TH400, and 4.10 gears, I get 11-12 mpg

[un4gvn!]

Originally Posted by 70STOVEBOLT

I think your gas gauge is wrong. If not, then WOW!

At 50-60 mph, my tach was fluxing between 3000 and 3700 rpm. I would watch the road and look down at the gas gauge and the needle moved an 1/8 of a tank. I would continue to watch the road for a little bit and look down and the gauge moved another 1/8 of a tank. Yes, I looked for leaks and any gremlins sucking on straws. Nothing. The next time I drove it to work, I never went above 50 mph. Had a 1/4 tank when I got home The first trip was a whole lot more fun. Isn't that what this is all about, fun? I'm NOT complaining.

[70STOVEBOLT]

Yep, fun is exactly what it's about for me. If I were worried about mileage, I would not have put in a big block.

[Tiger Joe]

67 C10. 496 BBC tremec 5 spd with 3.73s. Haven't got it out on the highway to try out the OD yet, but in town it gets 6

[davepl]

I believe the question in the olden days for my truck was "How far can you make it with the camper and big block and THREE full fuel tanks?", but I took out the two spares at restoration time.

I actually would have kept them if I drove it enough that the gas wouldn't all go stale, but I figured I'd never reliably burn 60 gallons in mine.

[XwalkerX]

L33 5.3L
4L60e
mid length headers
CAI
Blackbear Performance Tune
3.42 w/Eaton posi

currently 80% highway 20% city I see roughly 23mpg