tips for better MPG

[davepl]

I figured I should add that the nail in the coffin of the conspiracy guys (100mpg carb suppressed by oil companies and so on) is that if there WERE a way to increase MPG it would be hugely profitable for the big three.

Light trucks are being included in CAFE. CAFE is the average CORPORATE fuel economy, which means the average for EVERY vehicle they sell (other than HD trucks and whatever is excluded).

They'd all LIKE to be selling you SUVs, because that's where the money is. But they have to sell a bunch of low-profit sub-compacts (think Ford Focus) before they can sell a King Ranch Expedition (or whatever).

Meeting CAFE more easily would be like printing money. If they could, they would.

Completely unrelated: Did you know Chevy built over ONE MILLION full size cars per year in the late 60s? I mean Bel-Air/Biscayne/Impala/Caprice. What a monopoly!

[sleeper69]

just got my 69 on the road with a 496bb, 400th, 3.73, and im only getting 6mpg so be happy

[Eddie H.]

My 69 GMC with a 406 small block , TH400 trans and 3:07 rear end gets around 11-13 MPG

Fast forward 30 years, and my 99 GMC with a computer controlled, fuel injected, 5.7 vortec, 4L60E overdrive trans and 3:73 gears gets 11-16 MPG

Fast forward another 13 years and my 2012 Silverado with a 6.0 engine and overdrive trans still gets 11-16 mpg

In 43 years of design changes, fuel mileage is still not much different.
My unscientific conclusion is that It just takes a certain amount of fuel to push a heavy flat nosed truck, with the aerodynamics of a box car, through the wind.

[9teen69]

Originally Posted by Eddie H.

In 43 years of design changes, fuel mileage is still not much different.
My unscientific conclusion is that It just takes a certain amount of fuel to push a heavy flat nosed truck, with the aerodynamics of a box car, through the wind.

x2

[Coley]

...I think its pretty obvious how to resolve this.
I would simply go with Red Green's approach, he is clearly onto something:

Red Green ~ Toilet Power.flv - YouTube

LOL
Coley

[davepl]

I drove my 396 car from Regina to Ottawa with a brand new Holley vacuum secondary 3310. I got 8 mpg on the way there. I don't know how they come jetted from Summit or whatever, but it can't be that far off.

I put a Canadian Tire Q-jet on it and got 17 on the way back.

[i82much]

Originally Posted by davepl

I drove my 396 car from Regina to Ottawa with a brand new Holley vacuum secondary 3310. I got 8 mpg on the way there. I don't know how they come jetted from Summit or whatever, but it can't be that far off.

I put a Canadian Tire Q-jet on it and got 17 on the way back.

The Holleys are jetted just fine for WOT, the problem is they have about the same AFR at WOT as they do at cruise. A square bore is never going to be quite as good as a spread bore at getting optimal fuel economy, but there is no reason a properly-tuned 4150 of the correct size should not be within 10% or so of a Quadrajet in terms of mpg.

[preacher anthony]

I have a 69, 305,3.08 gears, 200r4 trans, HEI dist., Eldebrock intake, Holley 600 carb. Just got back from Holley Power Tour at ZMax. I got a little or 10. First trip w/ trans., I was expecting better. Someone mentioned going to 3.42 or 3.73 to stay in torque range. Any suggestions?

[nightmare]

Originally Posted by davepl

I can't agree there - the technology has not hurt mileage, it's only improved it. I'm not sure, other than carrying the weight of wires and chips, which is silly, how it could be otherwise.

Now on the weight part I agree. My Range Rover Autobiography weighs a good 2000 more pounds than my Longhorn (about 6800 vs 4800). And the hilarious part is all the weight savings - aluminum bodied, aluminum engined, titanium who knows what ... just to keep it at 6800!

Minimum base curb weight I could find for an F-150 is 4685, which isn't all that bad. And you'll max it out at 23mpg highway.

After all, at some point it requires a certain amount of fuel to move a a pound of truck against air drag.

Understandable. All I'm saying is that all the "technology:" airbags, computers, overall increase in size, etc., contributes to the decrease in fuel economy should be.

[nightmare]

Originally Posted by Eddie H.

My 69 GMC with a 406 small block , TH400 trans and 3:07 rear end gets around 11-13 MPG

Fast forward 30 years, and my 99 GMC with a computer controlled, fuel injected, 5.7 vortec, 4L60E overdrive trans and 3:73 gears gets 11-16 MPG

Fast forward another 13 years and my 2012 Silverado with a 6.0 engine and overdrive trans still gets 11-16 mpg

In 43 years of design changes, fuel mileage is still not much different.
My unscientific conclusion is that It just takes a certain amount of fuel to push a heavy flat nosed truck, with the aerodynamics of a box car, through the wind.

Yes, however, if you were to take that 6.0L from that 2012 Silverado, and place that into your 69 GMC, you'd probably be getting around 20-22 mpg in that same GMC.

[1972BlueC20]

UPDATE :

I drove very conservatively (like a grandma) on my last tank of gas and got 10.83 mpg. I think I can still squeeze a few more mpgs with some additional tweaking, but I'm not unhappy with almost 11 mpg for a 1972 3/4 ton beast. My 99 Tahoe only got 12-15 so it's not too bad.

Thanks for everyone's help and suggestions.

Love this forum!

[Eddie H.]

Originally Posted by nightmare

Yes, however, if you were to take that 6.0L from that 2012 Silverado, and place that into your 69 GMC, you'd probably be getting around 20-22 mpg in that same GMC.

Yep, I might do the LS engine upgrade in my 69 someday, just to see what it will do.

[aknovaman]

I did a tune on my buddies s10 blazer 53L 4L60e 342 gear rear and he is getting 23mpg and not even trying. I anticipate did to upper 20's once gets the cruise control hooked up and he stops doing burnouts.

[myyamr7]

I was getting between 10.5-11.5 in my 71 with a 402 and 200-4R trans, 3.07 rear gears, that is a mix of some highway, and around town. I bought a TCI converter lock up kit for the trans, and bumped the fuel mileage upto 13.5 doing the same driving. Amazing what a difference the lock up makes with fuel economy, and the overall quality of the ride the truck gives, plus cruising down the highway at 75mph at 1650 rpms is sorta funny

[502ms]

Well, let me throw something else into the mix. I have my 72 C10 which I get 18 mpg city, 20-21 mpg mixed city/hwy. On full highway I am getting 25-26 mpg - I have discovered this on my road trips in which I stayed in 6th gear and 5th gear with very little stopping.
My engine is 6.0 LS, transmission is T-56 6 speed, 3.73 rear gears, 27" tire, 20 gallon fuel cell.

[preacher anthony]

I have a 5.3 sitting in friends shop. Everyone keeps telling me difference parts that need to be changed to install. Some say u can use same oil pan, motor mounts and frame mounts off 5.3, even the stock manifolds. Too confusing, and my budget is too tight to afford unnecessary parts. 5.3 out of a Tahoe, good mileage on motor.

[engineer_gregh]

Wow, Leon thats some great fuel economy you're getting. If I rolled down a very tall mountain, in neutral, with my 71 BB 402, stock 400 tranny, and 3:07 rear end I could get that kind of fuel mileage. Oh, I would need to have the engine turned off as well when I was coasting down the hill:-)

[Lees68GMC]

Yup, I have the exact set up in my 68 Aknovaman, 5.3 from 2005 Suburban, 4L65E trans and 3:42 gears with 275-60-15 BFGs about 27" tall. I don't know what mileage I get around town as the exhaust sound is so awesome I've always got my foot in it.

Preacher Anthony the Stock 5.3 or 6.0 LS Truck manifolds won't fit (the outlets turn outboard right into the frame rails), but 2013 Camaro LS3 manifolds will they turn inboard and back. Tons of guys take their Camaro manifolds off and install long tube headers on their New Camaros so look on Ebay and Craigs List. Also stock motor mounts work (meaning the small block rubber components) But, you still need to buy motor mount adapter plates that bolt directly to the LSX block like those made by Hooker (yes the header company), the best fit & price about $79.00 from Speedway. The come in various models fromstandard engine location all the way up to 2-1/2" set back.

Also the stock mechanical fan is far superior performing compared to electric fans according to my friend, the manager at Ron Davis radiators, however you need to come up with a Big Block Fan shroud for our trucks for fit and clearance.

Hope it helps.

[preacher anthony]

Thanks, it sure does. What did u use for a radiator and did u buy a new computer or have the OEM redone?