What kind of fuel mileage is every one getting

[71CHEVYSHORTBED402]

I used to get 10. I've never checked since the rebuild in 1993, but I'm guessing 8-10. 23-25? My initial reaction is divide that by two, if you're lucky.

[GTSideSwipe]

Im getting around 10-12 mpg with the original 350 and Turbo 400 tranny with the 4.10:1 rear end.

[Steeveedee]

I get about 9 MPG running around town. It has gotten as high as 13 on a long haul without a trailer. It does push a lot of wind with that camper shell. My wife inherited it from her dad when he died. He used to have a '63 Chevy C10 with a 283 and 3 OTT. They would go camping all the time, but it took him 4 tries to gain the summit of Wolf Creek Pass in Colorado in it one time, because someone would cut in front of him and he had to slow down. Then, he had to turn around and go all the way to the bottom for another try. That 400/400/3.55 setup will pull stumps out of the ground, but going up Wolf Creek Pass I'll bet it would get maybe 4 MPG while gaining that summit. It's got 212+k miles on it (one rebuild at something over 100k) and I'm thinking that an LS would be a nice addition. I'll have to research it thoroughly first. I'd not like to go through all that conversion trouble for even 10 MPG, as little as it is driven.

[joeydurango]

Pre-LS swap, my stock-height/tire size '72 K10 350/350 got 10-ish MPG.

Post-LS swap, the same truck with a 2.5" lift, 33" BFG's, and a new 4L60e transmission got 16-19 MPG most of the time.

FWIW...

[kingstrider]

I get about 10-12 mpg depending on how heavy my foot rests on the fun pedal.

[BCOWANWHEELS]

12 mpg with my 250 I-6 13-14 WITH MY 383 n q-jet if I drive it very easy

[Alex V.]

'85 C3500 454/TH400/4.10's, bone stock from bumper to bumper, made many an empty trip to St. Louis and back (200 mi. round-trip) at 12.25-12.5 MPG. I did it enough times to experiment with 55 vs. 60 vs. 65 MPH, with tailgate up or down, and it made less than .5 MPG difference. And the speedo on it is accurate within 1 MPH.

'67 'Burb with a .458" lift cam in an otherwise stock '79 350 (4G carb.) w/NP435, 3.73's, and 30.5" tires - I only got a scientific check on it once, which I believe was 13.8. I haven't done a proper check since swapping in a calm cam ("290HP" - .383/.401 lift, I think) but I'd estimate it improved no more than 1 MPG. Though I'm not finished tuning on it yet and the drivetrain is far from fresh.

My parents' '97 2WD 1500 Suburban (350/4l60E/3.42's, 29" meats) lays right at 2,000 RPM at 70 MPH and has pulled 20-21 MPG on long trips, laden with luggage and running the A/C. Darned if it didn't hit 400,000 miles on the un-rebuilt Vortec 350 this fall, too.

[Mac's]

1968 C20, 307, 4 speed, 4.56 rear end, 235/85/16 tires,screaming at 60mph. If I drive around 50 mph I might get up to 10mpg

[toolboxchev]

Originally Posted by molinehotrod

I have 420 hp, 32 inch rear tire, 3.08 gears, 700r4 with 30% lower first gear and a taller over drive gear, i think it is .67. I think i am going to get 23- 25 miles per gallon.

If you getting that kinda mileage I invite you over to tune my engine. Then again I had leaned it out in the past, so you will not be allowed to do that trick

Seriously I believe you are getting good mileage with that setup. What do you know that will help the rest of us 6mpg rigs?

[Tdrcreyn4]

I have 69K20 with 396 naturally aspirated, 4.10 and 35's.......10mpg. Fun to drive though.

[lutronjim]

I put a LC9 with 4l65e tranny in my 70 c10. It has 3:73 rear end. 15" tires but I don't know height. Driving like grandma on back Ga roads at 60 mph it got 22.5 mpg. I had to go through three small towns but make most of the lights.

This was just over 110 miles as measured by gps - before I had speedo working. I filled up at start and end until auto cutoff.

Have measured around town but waaaay better than old 307.

[Saphiro]

My '69 C-20 gets a solid 10 mpg. I've gotten as low as 8 and as high as 11.5.
Growing up we had an '84 suburban that got a 454 for motor number three. With a 700R4 and habit of pulling car trailers the Aamco warranty was healthily exercised. Anyway, I remember doing everything I could to get better mileage out of it and my very best was 14.92 mpg, traveling at a modest 55 mph on level ground for ~200 miles. It never went below 10 mpg, however.

[Kell]

I know this is old but,

approximately 12.8 mpg for my I-6 3OTT driving the dog snot out of it, 50% in town

I would love for someone to chime in with a manual 4 speed overdrive conversion on their I-6, mine is pretty much screaming at 60mph. 20 years ago I had a stepside with just this conversion which did fine on the highway, don't remember the gas mileage though.

My 2002 2wd silverado doesn't do much better.

[Steeveedee]

Originally Posted by joeydurango

Pre-LS swap, my stock-height/tire size '72 K10 350/350 got 10-ish MPG.

Post-LS swap, the same truck with a 2.5" lift, 33" BFG's, and a new 4L60e transmission got 16-19 MPG most of the time.

FWIW...

Thanks, that is good to know.

[wesmigletz]

My 67 SWB with a 283/2bbl (all stock), 4 spd manual, 3.73 gears, 235/75/R15 gets 12-13 at 65-70 MPH.

My previous 67 SWB with a 350/TH350, holley low-rise single plain and 600 CFM Holley, 3.73 gears and a 29.5" tire got 15-16 mpg at 65-70. I spent a lot of time dialing in the idle feed restriction and my timing curve. The swirl port (pre-vortec) heads may have helped a bit, too.

[TwistedCycles]

I just figured mine up. Keeping in mind that I'm still breaking in this motor, I'm getting 12 mpg with a .030 over 350, flat top pistons, 194/1.50 heads(big chamber) .460 valve lift, edelbrock 600 cfm carb, turbo 350 trans and mid 80s power steering setup.

B.

[wreckedchevy]

I got 17 going to red lodge 2 years ago averaging around 60mph after we got the jets set just right (no more gas fumes) running a mild built 305 with edelbrock 650

[67shortstepside]

has anyone ever use or know anyone that has used the holley self tune fuel injection ?

[BCOWANWHEELS]

A melling mtc-1 towing cam really helped my mpg with my 383

[trac209]

Originally Posted by TwistedCycles

I just figured mine up. Keeping in mind that I'm still breaking in this motor, I'm getting 12 mpg with a .030 over 350, flat top pistons, 194/1.50 heads(big chamber) .460 valve lift, edelbrock 600 cfm carb, turbo 350 trans and mid 80s power steering setup.

B.

That's about what I get with a similar engine,my truck runs a 235/75/15 tire and has at least a 3.73 if not 4.10. Highway driving the engine is really up there in rpm. That said I've towed 2000 pounds with another 800 in the bed and it still gets the same lol. RPM is a key factor for getting good mileage. I have a Pontiac parisenne with a stock 305 qjet and plain lock up three speed auto and I can get 22 mpg highway cruising at 65-70 and I have got 23-24 if I keep it at 60 and baby it.

[YourBuddy'sTruck]

My 70 C20 with stock 350, TH350, and 14Bolt averages 10mpg....burdened or unburdened. Doesn't matter.

[special-K]

I get better mileage in my '72 K2500 350/TH350 4.10 than I do in my '95 K2500 350/4L80E 4.10 Suburban. 12.5 vs 10.

[BCOWANWHEELS]

I noticed a "c" class benz only advertises 17 mpg

[joecaruso]

I get around 14-16 in my 70 C-10. It has the stock 402 and three on the tree transmission and I believe 3.73 rear end. Granted I drive pretty conservatively and rarely crack 2500 rpm.