There is a sweet spot for every vehical. The 65 mph speed limit is, more so was, based of fuel ecconemy. Cars were generaly set up to run 65 at max efficiantcy.

Most of my driving is in town and fairly short hi way trips(25 or less each way).

 

Well, if you pull 2k at 45 and the same 2k at 65 in a higher gear, you are traveling more miles in one hour and burning the same amount of gas. At least that's what I have experienced.

 

As long as you aren't loading the motor really heavy to pull those same rpms at the higher speed. That is the key like I said finding the sweet spot if you really want to get the absolute best.

RPMS mean very little for actual fuel millage. Load is the biggest factor. Pulling a trailer is a perfect example. On level roads the bigblock runs 65-70 no problem doesn't downshift ever and rarely unlocks the converter. It is still spining the same rpm as if it were empty. Extra load on the motor takes extra fuel to keep that load moving.

 

What gears are in the rear axle?
How about a gear vendors OD unit? They are around $2,700

You might pick up a couple MPG, but you'll never recover the cost of the OD with the savings.

It might be cheaper for you to sell this truck and buy a newer (not new) truck with a more efficient drivetrain.

 

Thats more than likely the best option. In the end your gonna be lucky to hit double digit MPG, its a big block and all it was made for low end grunt, never was gas mileage thought of. Tune and gears are the only things that are gonna help. Lean it out some and make extensive use of the EGR (if you can, or if it even has EGR). Get some ridiculous low gears, like 2.43s or so. If something gives you more power then it WILL NOT give you better MPG, intake, exhaust, whatever. THERE NOT GONNA HELP, and there only gonna make it worse. If it makes it easier for air to go in and out, then stay away. More air, then more fuel, simple as that.

 

You clearly have no clue obout efficiancy. More hp means the motor is more effieciant. Now when you make extra hp that isn't needed to simply drive at a normal pace you are going to drop fuel efficiancy. I don't want to turn this thread into a big debate and have to educate everyone who doen't understand fuel effeciancy because the point of the thread gets lost.

Please follow my upgrades watch the gains in fuel ecconomy and learn what helps, what doesn't and how much change they make.

 

Buying a newer truck will not help and make a big hole in my pocket. It isn't going to get much better ecconemy and I will have the payment that would WAY more then offset the few MPG gain. Again i bought the truck because I NEED it. I didn't buy it for any other reason and certainly didn't buy it for fuel ecconomy. But if I can invest a few dollars hear and there, make that money pay for it's self in a reasonable amount of time and then save some money 3000-5000 miles down the road that is money well spent. Also it allows me to get some real world proof of what helps and how much. Also what might not help.

 

I agree, I was assuming the truck was under the same conditions at both speeds. Even if your pulling 5000 lbs up a 30%grade, if your going 45, your buring the same, maybe more, gas than you would be pulling the same weight on the same grade at 65. I had a '91 454ss, and it always got 12 or 13 mpg under all conditions. The only time the mileage went down is when I had bad gas in it.

Do you have e-fans on the big block? That could help, I have been considering doing that myself on my 6.0l. Takes that extra load off the engine.

 

Efans are part of the plans.

I am hopefully apllying for/buying a house so every spare penny for the next month or two is going to cover all of that. So I will do my best to use the best fuel ecconomy mod of all!
COMPANY TRUCK!!!!!!

 

No clue? Yeah. I wouldnt be telling you this for no reason, more hp comes from what? More air and FUEL. Add your intake, remove restrictions in the intake tract, and more air will go in. Its not very hard to comprehend. Get a tune, lock up the TC earlier and lean it out everywhere (dont go crazy), and good luck.