Can't believe this gas mileage

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Ron Sebastian

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Except the 4 gallon mark is each quarter so to get 10 gallons in the tank you need to be closer to the 1/4 mark. I drive mine daily to get 10 gallons in, I’m closer to the 1/4. To get 13 gallons in, I’m scary close to the empty mark.
When I fill up, the Needle goes to the top of the F. You probably have more gas than the gauge shows.
 

eskimomann209

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When I fill up, the Needle goes to the top of the F. You probably have more gas than the gauge shows.
It is probable. It’s your truck I figure you probably know how many gallons your tank is. Congrats on the mileage. My LS swap is roughly that on a soft food day. Those are few and far between lol
 

Snoots

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Not quite what I thought but still pretty good. The truck has 16 gal tanks just to assure everyone. Drove 172.5 miles, gauge read just under half a tank see pic. Fueled up and pump read 9.928 gallons, so I'm thinking gauge is pretty accurate. 17.375 MPG is what I come up with.
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Food BAG!? Are you kidding?
 

Kim Burke

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Don’t mess with it, whatever you do! I’d run the thing down to 1/4 with a can in the bed for safety just so I could know for sure. Regardless, that’s awesome results.
 

Ron Sebastian

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Don’t mess with it, whatever you do! I’d run the thing down to 1/4 with a can in the bed for safety just so I could know for sure. Regardless, that’s awesome results.
I can run it dry, then switch tanks. The beauty of having two tanks. I hear it's not good to do that though. I like to fill up at half tank, it's a military thing.
 

Frankenchevy

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What gearing and trans do you have?

Is it pretty flat where you live?
 

SquareRoot

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I got 20 gal tanks on my Longbed K20. I filled it up when it dropped to 3/4 tank. Took 11 gallons. So much for linear regression.
 

RecklessWOT

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Not factory. LMC tach conversion. Adds tach in place of giant gas gauge and places the small gas gauge in the original unused spot.
That's cool, I never knew LMC had an aftermarket kit for that. Looks stock, I was fooled lol. I've seen a gas gauge in that spot on trucks that came with the optional factory tach where the big gas gauge usually is, and I've also seen them come with an optional factory clock in the "blank" spot.

I'd love to do that conversion to my truck, but I have no room as I've got a B&M trans temp gauge there because 700R4 :/
 

CORVAIRWILD

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Fuel mileage is a very tricky thing. There's only one way to accurately measure it, and even that way has its shortcomings. Drive a certain amount of miles, make sure the speedometer is accurate, and then fill it up with the same amount of clicks after it's full.


I always always always check my fuel mileage, I've been doing it since I first started driving, because my father always did it. And I drive across the country two or three times a year, and there's times when I do the exact same fill up routine, and my mileage will drop 10 or 20%, or be 10 or 20% higher. And I have no explanation. From one fill up to the next I'll go from for example 15 MPG, to 19. The next fill up will be back down to 15. Makes no sense whatsoever, but one thing I have noticed, is when I just put in a gallon or two or three, the mileage can vary drastically. And the reason I only put in a gallon or two, it's maybe because the fuel price in the next state is a lot higher, or I want to have it full when I start off driving the next morning.

So I never take it seriously unless it's a half a tank or more, usually the best is when the tank is empty. The margin of error seems to be less.

My 2008 G5 has an electronic fuel mileage counter, and by the way NONE of these actually measure the fuel going through your engine, they're using an algorithm based on computer simulations in a lab. And I check my fuel mileage every fill-up, and I drive the car a lot, and sometimes it's within a very small error, and sometimes it's off by 5%. So no explanation for that either except that like I mentioned, it's not the actual fuel passing through the fuel line it's measuring, it's just checking all the parameters and basing the dispay you see on a computer model.

Back on topic, my '84 6.2 diesel Suburban with a 700 overdrive and no lockup gets around 16 17 at 60 miles per hour. It's a four-wheel drive 3/4 ton, and my 6.5 turbo diesel pickup truck used to get around 15.5 or 16 with lock up. So less heavy pickup with a turbo diesel would get slightly lower fuel mileage. And my '95 6.5 turbo diesel 3/4 ton four-wheel-drive Suburban got the exact same mileage as my '84 6.2, even though the '95 Suburban had lockup, and my '84 lockup wasn't working at the time. Now I have a rebuilt transmission with a hydraulic lock up in the '84 6.2
 
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CORVAIRWILD

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Here's an example of crazy numbers. I filled up my 4-cylinder 5-speed G5, it was down to about half a tank, the tank holds 11 gallons. And go figure out why I was getting 12 miles per gallon, usually gets 28 to 32.

To go over the math, I did 60 miles, my odometer is accurate, I checked it, and I used 5 gallons = 12 miles per gallon.

I realize cold starts and short trips kill mileage, but down to less than half? That's why I said you can't always rely on anything

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