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Old 06-19-2017, 02:42 PM   #1
eighteenninetytwo
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Best way of improving MPG?

Seems like I'm getting about 8PMG right now. it seems to be running a bit rich so I will adjust the carburettors a bit and might eke another MPG or 2 out like that, but are there any obvious ways of going about this (short of a new transmission with overdrive) that I should consider. Is it possible to change front and rear diff ratios by changing internal components for instance?
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Old 06-19-2017, 06:29 PM   #2
SilverMiner
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Re: Best way of improving MPG?

I have a large collection of old magazines covering the era of our trucks (late 72 to mid 84-ish) such as Four Wheeler, Pickup Van & 4WD, Four Wheel & Off Road, and even some of the oddballs. By far the most covered subject is fuel mileage, which is no surprise considering the oil crisis in 73 and then again in 79. Back in the day, 8 to 10mpg was about what they got from real world testing. And their fuel was better than ours today - it still had lead until the late 70's and obviously no ethanol. Another big advance during the time period was radial tires with better rolling resistance than the standard bias ply's of the day.

Jump ahead to the 21st Century, and we are all running radial tires, probably with no smog equipment attached after four decades of use, but having to buy inferior fuel with less energy per unit volume. In my opinion and past experience a well tuned V8 in one of our squarebody rigs should hit low end double digits for mpg with 10 being the bottom for a cruising trip. Low speed trips in the woods or around town will easily dip into the upper single digits with 8 being the worst I'd plan for or expect.

Modern improvements can be found with fuel injected LS engines and computer controlled transmissions, and fortunately enough those also come with performance gains, but the installation cost will never be offset by fuel savings in a reasonable amount of time.
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Old 06-19-2017, 06:40 PM   #3
eighteenninetytwo
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Re: Best way of improving MPG?

Yeah - I have looked at the cost of a 7004R transmission and the savings on fuel - even if I got 50% more MPG - would never be offset. I guess tuning the carbs and actually inflating my tires properly would help the most
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Old 06-19-2017, 09:13 PM   #4
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Re: Best way of improving MPG?

I started doing alot better MPG after installing an Autometer Air/fuel ratio gauge. Became much easier to pass the IM test here too. Only thing is I switched to a carb that would let me tune easier. The Q-jet has never done me wrong, but I couldn't change jets and metering rods very easy. I chose the 625 street Demon with the re-jet kit. Took quite a few tweaks, but I'm getting a pretty consistent 15mpg now. Better power on the hills too. Obviously, over 8,000' is a different tune for that of sea level and takes a few minutes to make the change.
I was real close to going with an EFI throttle body, but using a tunable carb with a A/F gauge is the way to go IMO for one reason; so I can work on it if I need to. The only thing that prevented me from going with the Holley Sniper was that if it failed I was sending it to Holley for repair. That's not an option for me while on the side of the road somewhere. If a carb fails I can diagnose, fix it, and move along. Factory 4 speed, 35's, 3:73's.
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Old 06-20-2017, 01:24 AM   #5
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Re: Best way of improving MPG?

Drive slower. Lol! I just completed a 3000 mi trip and kept my speed around 60 mph (engine turning over at 1250 RPM) and averaged 29 mpg with the rig in my signature. Also had my tires pumped up to 80 psi.
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Old 06-20-2017, 03:30 PM   #6
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Re: Best way of improving MPG?

Properly inflated tires helps.
As does hooking up a vacuum gauge you can read easily and driving at the highest vacuum.
And maximize your initial timing. As well as your vac advance.
And make your apt adjustable in the carb.
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Old 06-20-2017, 05:37 PM   #7
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Re: Best way of improving MPG?

Quote:
Originally Posted by Edahall View Post
Drive slower. Lol! I just completed a 3000 mi trip and kept my speed around 60 mph (engine turning over at 1250 RPM) and averaged 29 mpg with the rig in my signature. Also had my tires pumped up to 80 psi.
Yeah, but that's like cheating with the 12V. Braggart.
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Old 07-14-2017, 03:23 AM   #8
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Re: Best way of improving MPG?

Best thing I did for improve gas mileage was a LS swap 7 gallons gas Visalia to Paso Robles
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Old 07-23-2017, 11:55 PM   #9
72MARIO
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Re: Best way of improving MPG?

Ls swap would be the most worth while swap. Not only do you get better mpg but the driveablity is greatly improved.
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Old 07-24-2017, 05:47 PM   #10
eighteenninetytwo
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Re: Best way of improving MPG?

Yah - but an LS swap costs how much??? For every thousand dollars I spend I could drive another 2280 miles at 8 mpg and @ $3.50 per gallon.
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Old 07-24-2017, 06:06 PM   #11
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Re: Best way of improving MPG?

Around $2800 into my LS swap and I haven't had one regret yet power gas mileage starts on dime
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Old 07-24-2017, 08:04 PM   #12
eighteenninetytwo
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Re: Best way of improving MPG?

hmmm - better than i thought, but is that doing it yourself - My problem is i dont have the tech skills OR facilities / capacity to deal with that - i would be paying probably $100 per hour (in CA) to get it done. that might be the killer.
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Old 07-29-2017, 11:36 AM   #13
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Re: Best way of improving MPG?

1982, you didn't provide any information about your vehicle. So generically speaking you need to check to see what has been modified on your rig. Does it have all the vacuum hoses hooked up correctly, does it have an aftermarket carburetor(s) (which is most likely set up rich), is the timing set correctly, has the advance curve been optimized? Check and repair or adjust all of those things and then do what you can to make the vehicle roll easier. That would include taking extra weight out of the vehicle (tools, tire chains, etc.), make sure the tires are properly inflated and are not overly wide. Check the gear ratio of the rear axle and if it is low (numerically high) will have a huge effect on mileage. You can help the gear ratio with a change in tire size (if it is too low use as tall a tire as is practicable, and correct the speedometer)

If it still has the Quadrajet carburetor it can be tuned to be very efficient.

After all the tune up has been optimized your driving skills need to be optimized for fuel efficiency.

After all of that you will still not have a vehicle that was designed for fuel efficiency, but it will be a cheap to maintain, useful vehicle. Economy isn't about just fuel mileage.
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Old 07-29-2017, 02:39 PM   #14
eighteenninetytwo
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Re: Best way of improving MPG?

Wow. That is a ton of really good information and ideas. I am a total beginner at this stuff, so need to research all of this detail on the vehicle and report back.
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Old 07-29-2017, 05:03 PM   #15
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Re: Best way of improving MPG?

I like to keep things simple. Seems like it would take a lot of mpg improvement to makeup for a new engine. I didn't buy a k5 for good gas performance anyway. I'd stick with the original engine and tune the quadrajet. Easy to work on and keeps things simple when you go to autozone for parts. Just my two cents...
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