How bad is my gas milage?

[the-wreck]

Hey all
I just started driving my 68 shortbed (w a 350) after a ong restoration. I was a little surprised at the gas milage. It seems I can almost watch the gas gauge go down as I drive. Are our trucks that bad? I havnt calculated the milage but I will (Im kinda afraid to).

[ckhd]

I get 7 in the K20. 10 in the 'burb.

[JimKshortstep4x4]

Not sure what you are getting but 14-16 mpg is pretty good. Some get 10-11 and a lot depends on how you drive. The gearing has a lot to do with it. I take it that the engine has been rebuilt
and if so the mileage will improve some as you drive it.

Jim

[Ackattack]

I get around 10 or 11 on the highway. In addition to gearing, your cam and carb affect your mileage.

[Huck]

What are you worried about? On Long Island you drive 3 minutes and you are in a traffic jam and with the gas costing you $1.75 a gallon, who can afford to drive more then one or two miles anyway??!!

[AndrewDT]

On the road trip to Pigeon Forge last year I got 15 mpg with my Suburban. To get that I drove about 52 mph down hill with the wind, but I was happy. Around town when I'm in a hurry... I'd rather not think about it.

[AndrewDT]

To complete my restoration, I need to redo the engine but I'm afraid to rebuild it. I know the mpgs won't get better.

[rigo]

8-10 mpg on mine.....sometimes lower.....depends on how much gravity pulls on my foot that particular day.....hehehe.......

rigo

[junkyardjohn]

MY 1 TON TOW TRUCK IS GETTING BY FAR, THE BEST MILEAGE OF ANY 67-72 TRUCK I'VE EVER OWNED, & I'VE BEEN DRIVING THEN EXCLUSIVELY, EVERY DAY, FOR 18 YEARS. IT'S GETTING 14.7 MPG WITH A TIRED, PROPERLY TUNED SMALL BLOCK & A 4 SPEED. I'VE TALKED TO PEOPLE THAT SWEAR THERE GETTING 20 MPG, BUT I FIND IT ALMOST IMPOSSIBLE TO BELIEVE. H@LL ONE GUY ON THIS BOARD SWEARS HE PICKED UP 3 MPG & 20 HP BY SWITCHING TO AN ELECTRIC FAN. LOL. MY CURRANT PROJECT IS A 72 SHORT FLEET CHEYENNE.WITH A SMALL BLOCK(THAT I'M BUILDING FOR FUEL MILLAGE) 700R4 TRANNY, & A FORD 9" WITH 3.00 GEARS, & MY GOAL IS 20 MPG, & I THINK THAT IS PRETTY OPTOMISTIC.

(PS. PEOPLE NEVER SEEM TO UNDERESTIMATE H.P. OR M.P.G.)

[Longhorn Man]

In my old Longhorn, (3/4 ton 350?TH350 W/456 gears) I was able to get 14 MPG once...My engine is built to live in a higher RPM range and runs best (most efficient) at about 3000 RPM. I slapped the same engine and tranny in my SWB 1/2 ton GMC (3.07 gears) and get about 7-8 in town and 13 freeway at best.
I'm afraid to find out what the one ton Longhorn will do with (suspected) 4.56 gears and the 425 Caddy big block.

[the-wreck]

Thanks guys.
I was surprised at my poor milage especially since I have been driving gently so to speak. I have headers,performer intake cam and 600cfm edelbrok carb on it. I forgot my gear ratio but from the sound on the highway it sounds something likelike 3:70.

Huck-your kill me,LOL, I leave for work early early so I dont hit any traffic and I stay off the roads during the day so my traffic problem are not too bad. Farther west its pretty bad though!

[mtdave2]

i think 10 is about average. i get from 10-12 with my longhorn. but i did get 17 mpg when we moved down here. that was going about 45mph on the high way! (was stuck behind the reallly slow uhall truck)

[Andy4639]

I have put a 86 305 TPI with a 700-R4 trans. I get about 14-16 around home, and 18-20 out on the highway.

junkyardjohn

If you plan on the 700-R4 with 3.00 gears I would think you should get at least 20 on the highway. I still have the factory 4:10 in mine. You can check it out in my signature.

[Longhorn Man]

Remember, lower gears does not ALWAYS mean better MPG... just most of the time.

[kxmotox247]

I have a 68 CST with a 396/400 and low gears. 9 mpg before the HEI distributor. 10-12 after. It doesn't matter...highway or town...trailer or no trailer. I would say that 10 mpg is my average because I have a heavy foot in that truck.

[Estanley]

When my truck was together I never got better than 6 mpg. That's 350sb with a 3.40 or so rear, speed trans and one lead shoe.

[68 Suburban]

15+ for me.

[jmil1974]

With my old 350, I could get 12-15 city and 15-20 highway. I have a TH350 and 3.08 rear. Too few miles to tell for sure now with the "new" motor but it's feeling like 10 no matter what. I think my Torker manifold is killing me.

[Blue68]

Let's compare....A 2003 Chevy Silverado is rated at 14city and 19/20 highway with a V6 fuel injected engine. The weight is very comparable to our trucks and they (unlike most of us) run overdrive trannies. And I'm guessing these are the best numbers put up with the 3.08 rearends (where most of our trucks were built with 3.73 rears).

Just some numbers to think about.

[Huck]

MPG is usually a factor of HP, RPM, weight, gears, wind resistance and foot. My 72 1/2 ton with crate 350, edelbrock 1406, edel performer, headers, HEI, 308 rear and 96 5speed, will give me 20+mpg on the flat highway but will mean downshift on hills if towing.
Lovemuffins Grand Caravan AWD gives us 20+ mpg highway.
My 97 Corvette 6 speed gave me 30+mpg highway all the time.

I wonder how a six banger with a 3 speed does?

[68 Suburban]

Originally posted by the-wreck
Thanks guys.
I was surprised at my poor milage especially since I have been driving gently so to speak. I have headers,performer intake cam and 600cfm edelbrok carb on it. I forgot my gear ratio but from the sound on the highway it sounds something likelike 3:70.

Huck-your kill me,LOL, I leave for work early early so I dont hit any traffic and I stay off the roads during the day so my traffic problem are not too bad. Farther west its pretty bad though!

I had to tune the 1406 to position "12" on the following chart. The 1406 is way to rich out of the box for a stock engine.

[mikep]

my old 250 6 banger '69 with a 3 speed got 18 mpg on the highway .

I also think anyone claiming 20+ ( its the "+" thing that kills me ) out of a V8 in one of these either is full of it OR their Truck is a complete dog to drive.

Mines well tuned, tall tires and 3.54 gears . Of course it does tip the scales at 4450 lbs empty . I get 10 in the city and nearly 13 on the highway. That is at least until next week when the 274S Cam gets installed. Then it all goes to hell in a handbasket.

[jku72]

Okay, I always read about who say you HAVE to get crap mileage or your lying. I feel bad for them. I have calculated by gallons used, highway milage for my 68 burb with 4 speed and 3.08 gears at 19.8 MPG. There are several reasons, one is great tuning, the second is a healthy compression ratio, with proper cam for milage, and the biggest reason is the gears. I was getting the junk mileage that others talk about till I switched the rear gears. But it is not all gears, as my 1 ton longhorn gets 14.7 on the highway with 4.10 gears and a 402 auto. Of course around town it is not near as good, and I have not calculated around town on either truck, so am not sure how that helps. I will also tells you that the figures for the burb are at 60-65 MPH, and the longhorn was cruising at 55-60 MPH.
It is easy for me to see how a guy could get 20 MPG, if you do the setup right. EASY!!!
One important note, higher compression gives better power AND mileage. Spend more time figuring out how to run high compression and 87 octane, and you will get the mileage.

[68 Suburban]

jku72, what are the specs on the cam you are using?

[lukecp]

I have been averaging 10.4 MPG with 50/50 highway/city driving on my truck. The engine is a 16k rebuilt 350, stock heads, RV cam, 8.5:1 compression, Edelbrock intake, 1406 carb, and headers. I also have 3.07 gears and 27" tall tires. When i had a Q-jet carb on the truck i averaged around 13 mpg, and i didn't think that was too bad at all for a mild 350 in a 4000 lb truck. The Edelbrock carb does run a little better, but the mileage dropped off quite a bit.

I jetted it a little leaner last week, and i am gonna see how much it affects my gas mileage. If i still cant break the 12 mpg barrier, i am gonna get a JET Quadrajet.

This summer i also might put a new set of heads on it, which will bump the compression up to about 9.6:1, and give me quite a bit more power .