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View Full Version : How many MPG do you get with a full tank?

06-19-2001, 01:33 PM
I'm just currious but how many MPG do you guys get to a tank.. on average..
It seems like I only get 100-130.. and I have a 24 gallon tank...I'm going to run it out of gas to get an accurate reading but still I'm currious to other rides gas mileage...

85 Jimmy 4" Lift, 3" body bought have not installed yet, Dana 44, 14bff,
37" SSR's Yes they FIT with a 4" lift and don't rub.

06-19-2001, 01:50 PM
Straight highway I got 410 miles and the tank took just over 29 gallons to fill. That was my best tank, but I've come close to that a couple of times now.


<font color=green>Dyslexics of the world...UNTIE!</font color=green>

06-19-2001, 01:55 PM
That's only 4-5 MPG, if you're putting 24 gallons back into the tank. Unless you have a monster big block under the hood, that's pretty pathetic mileage.

You don't have to run your tank dry to determine your fuel mileage. Just fill the tank and note the mileage (we'll call this MilesBegin). Drive until you're down to 1/4 tank or less and then fill the tank again. Note the amount of fuel that it takes and note the mileage (we'll call this MilesEnd).

Now Subtract MilesEnd from MilesBegin to get your total miles driven since the first fillup. Divide the total miles driven by the amount of fuel you needed to fill the tank the 2nd time.

For example: 125325 - 125025 = 300 miles travelled. If you bought 20 gallons of gas to fill the tank, then 300/20 = 15 MPG.

Note that if you've installed larger tires but kept the stock axle gears, then your truck is going much further on a tank than you might think due to speeeometer error. If the speedo reads slow by 20%, then the odometer will only show 80 miles for every 100 miles that you've actually driven. This will make you're mileage seem worse than it actually is.

<font color=black>HarryH3 - '75 K5</font color=black>
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It's a great day to be alive...

06-19-2001, 02:09 PM
I'm getting around 11 these days.


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06-19-2001, 02:25 PM
I have an 85 Jimmy as well with a 305. With A/C I get 10-11 MPG. Without, I get 12-13 MPG. I have a 31 gallon tank, but can only get to about 27 gallons of it. Hence, with that all said, I can safely get 250-275 miles on a tank.

85 GMC Jimmy, 305 w/TH700-NP208, 32X11.5 BFG ATs, 15x10 Eagles, Smittybuilt tube nerf bars and bumbers

06-19-2001, 02:30 PM
I've made it just over 400 without refueling, on a 31 gallon tank, running strictly highway. In town, I would guess around 250.

I'm so poor I can't even pay attention
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06-19-2001, 03:02 PM
87 TBI with over 110K 700r4 31" BFG's with 3.42's. I get 14 city and better than that highway. The high flow cat and flowmaster got me there. I'm hoping the k/n filter and tune up will get a little more.
Ben 87 Jimmy
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06-19-2001, 03:17 PM
My truck is always thirsty. I get about 230 on a tank as an average. It's a 21 gallon tank. If I didn't leadfoot it, I'm sure i'd get better

Mud Bath
06-19-2001, 03:32 PM
i get about 14.5 mpg running premium only about 11 with reg.
i can go 400 miles to the tank (31 gallon tank). 88 k5 tbi 3.73 gears and 33's

06-19-2001, 04:46 PM
I get about 12 in the city and around 15 or so on the highway. Best MPG was on the highway(s) from Arizona to Texas. Was doing around 17. I have the 31 gallon tank. Bone stock truck with SM465 tranny and 3.42 gears. Itali83 ... what brand did you use for the hi flow cat and what series on the Flowmasters? I'm thinking of doing this myself.

06-19-2001, 05:05 PM
I orderd it all out of (></A>)

06-19-2001, 06:18 PM
This is when I had 36" tires... I had 3.08's gears, and a 350... 31 gallon tank.... and a very heavy lead foot! I get about 310-345 a tank.....

Now that I have 33's I haven't really compared but it's actually worse if you can believe that... I think i get 290-310....

"Suck Fumes Ford Boy"
"I love my country, I fear my government"
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06-19-2001, 06:25 PM
Yes, it is hard to believe !
Just curoius how do you'all measure the milage ?
I assume you measure the gas ? By the pump !

06-19-2001, 06:33 PM
I write down the number on my odometer what mileage I have... then I fill up the tank full to the top... then I drive it til it's fumes. I write down the mileage and subtract the mileage when I filled up and divide it by 31.... always has worked well for me. I'm sure it's not perfect but it's close because like I said I literally know I have had an 1/8 of a gallon left because I checked how much gas I got on the next fill up.... make sense?

"Suck Fumes Ford Boy"
"I love my country, I fear my government"
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06-19-2001, 06:33 PM
I get about 17 mpg and about 490 per tank.

1984 GMC Jimmy 379 diesel, 700R4, 3.73s, 31 x10.50 x 15

06-19-2001, 06:37 PM
Yes, and No.
The No part is you milage(miles travel per tank) is not correct, therfore the result is not correct.
So if you want any accuratcy you need to have accurate miles.

06-20-2001, 07:35 AM
1989 350/700R/33X12.5.....26 gal. tank....325 miles/tank. Avg is 12.6 mpg.

85 Burb and an 89 Blazer
One just for fun, one simply for pleazer

06-20-2001, 07:53 AM
I get 0 or infinate mpg??? how would you look at that? No tank and it's been sitting for nearly 2 years. Although I've got a new shiny 20 gallon fuel cell waiting to go in. will let you know mpg then!!!

Sherman, Tx
<font color=red>Come Awn yall...Let's go to LUCHENBACH, TEXAS!!!</font color=red>

06-20-2001, 07:54 AM
Buddy, I don't know what your problem is, but your posts aren't very friendly. Do you really drive a J**p or something?!?

Anyway, if you have a full tank of gas and record your odometer reading. Then, drive as much or as little as you want. Then stop and fill it up again. You have to fill the tank again. However much gas you put in is the amount of gas you consumed since your last fill up. So, check your odometer again. If you travelled 250 miles since your last filup and put 25 gallons in the tank this time, you got 10 MPG since your last fillup. If you have a 31 gallon tank, this presumes you will get 310 miles on a tank (31 gal x 10 MPG, simple math, and if you are willing to run it dry). I know with my tank, from experience, I can only get to about 27 of the 31 gallons. I know this because I have run out of gas before and when I filled it up, I only put 27 gallons in it.

So, there's the math. If you have a problem with that, take it to another website. If you can't seem to offer help, only attack where you think people are wrong, I certainly don't want any of your replies to my posts. But, if you have something constructive to offer, please feel free.

85 GMC Jimmy, 305 w/TH700-NP208, 32X11.5 BFG ATs, 15x10 Eagles, Smittybuilt tube nerf bars and bumbers

06-20-2001, 09:01 AM
Yall may not believe this, but I get like 300something a tank (26 gallon tank) on my 89' with 36" Swampers and 1 ton axles. I have 4.56 gears. Bone stock 350 (except it has a K & N; but that's not really a mod) and 700R4 trans. This is combo with highway and city driving and I get very close to 13 mpg. I love it!!

89' 1 TON of FUN K5

06-20-2001, 10:59 AM
I get an average of 350 miles between highway and city with a 31 gal tank. The emptiest I had the tank was 1.5 gal. I had to be very carefull when I turned a corner.

06-20-2001, 11:35 AM
I just got back from a 150 mile trip, and according to odometer, did about 13 mpg going there via highway nonstop and around town until jumping back on the highway and re-filling. According to odometer, though, which I know is slow. I'd guess I'm probably getting 15mpg on long trips like that (lotsa highway). 33"'s, 350 TBI, stocker.
Like many others have said, I agree; you just need to keep filling the tank and tracking how many gallons you dump in each time, and how many miles you've gone since last fill-up (I know this works; my sender's malfunctional). The key is fill up, though.
Also, running down to empty isn't good on FI trucks, because it will run the in-tank pump dry, which shortens it's life (been there too many times before deciding to just keep the tank full).
On my old K5, my speedo cable died, then my fuel sender wire broke off the assembly (actually the pump power wire broke off, but I sacrificed the sender wire to pump power). Try figuring out mileage with that combo!!

You might actually have the 28 gallon tank, and not the 31 if you can only refill it to 27 gallons after going dry. If you definately have the 31gal, I'd say yank out your sender assembly and make sure somehow the pickup/inlet isn't short, and not reaching the 4 gallons in the bottom of your tank.

**<A target="_blank" HREF=></A> What more is there to life?**

06-20-2001, 11:38 AM
[purple ]NOT ENOUGH !!!!!!

. Riz . <A target="_blank" HREF=></A>

06-20-2001, 12:06 PM
I have a 31 gallon tank too, and run it out of gas all the time. I always seem to put 27-28 gallons in when I fill it up all the way...which I never do. Have put 33 in it before.....??? Gas gauge is really wierd, if its on empty and I put $10 in, roughly 6 gallons, it goes to almost 1/2 full.....


See my truck at <A target="_blank" HREF=></A>

06-20-2001, 12:16 PM
You misunderstood my post .
If your odometer is at 10983, and you travel to 10999, who many miles have you traveled ?
Now the fun part, 33, 36, 38,.. 31's, gears(ring and pinion) , odometer gears ?
Take these varyables into account, and you will not have accurate miles traveled !
Hope this meets your approval.

06-20-2001, 01:40 PM
Damn odometer... and Damn gas gauge.....

I have 37's and 3/4 tons with 4.11's (i think)
But it seems like I can't get any kind of accurate reading...
When I fill up my tank, the gas gauge goes to about a little past the 3/4 mark... When I use to fill it up to the max it would go to about 1/4 past Full... so I'm gonna run the damn thing dry till I find out exactly how much off the gauge is....

85 Jimmy 4" Lift, 3" body bought have not installed yet, Dana 44, 14bff,
37" SSR's Yes they FIT with a 4" lift and don't rub.

06-20-2001, 01:45 PM
I,v never ran my tank bone dry to test the range but I,v got over 400 miles out of my 31 gal tank before I filled it up. I'v checked my spedo on a measured mile and it is right on. And it came set from the factory for the 31s I am running. On my last trip to Carson City I got 20 MPG on the freeway traveling around 70 mph. 350 miles on 17 gals of gas.
I'm running a TBI 350, 700r4, 3.73s, headers, K&N,flowmaster, MSD, ECT. It seems the more performance I bolt on the better my gas mileage gets

06-20-2001, 02:37 PM
Cool, now this sounds reasonable !~

Now, make some mods(changes) to the tire size, and the gears.
The gas gauge, and the odometer will not change their reads, but the distance(true miles) will change !

<P ID="edit"><FONT SIZE=-1>Edited by Executioner on 06/20/01 02:53 PM (server time).</FONT></P>

06-21-2001, 10:28 PM
Just a heads up on exhaust mods. If you will need a muffler shop to do some of the work make sure that your setup is legal or that they agree before you get your components to do the work. In ID they can't do any work that doesn't meet smog specs. I asked them about it when them modded my exhaust route.

06-23-2001, 01:38 AM
Is your speedo accurate?

'84 Chevy K10, lifted, loud, fast, and 3/4 ton axles

06-23-2001, 02:55 AM
i get about 11 miles per gallon. Please tell me what yall do to get better milage please help might have to sell soon if i don't. I have to fill up every other day and the worst part is it is only a 305 it like there unburned gas just pouring out exaust already rebuilt carb too please help.

06-23-2001, 03:21 AM
It really all depends on your setup, but I get about 11 mpg too, maybe 13 if I drive like a grandma.

'84 Chevy K10, lifted, loud, fast, and 3/4 ton axles

06-23-2001, 03:53 PM
Mine does much better on the trailer than on it's own tires. I'm guessing about 5-6 mpg. that's a mix of 'wheeling, town and freeway. Not ever much more than 70mph. Ouch.
Previous buildups had no problems getting 13 or so consistantly, as long as the gearing and tires matched up to the speeds I was driving. Like with 4.56's and 35's, it did pretty good, I could use the overdrive and go 70 or so before it really headed downhill. With 37's, the same combo wouldn't pull 4th very well so it was worse.
Remember, ride height kills you for milage at higher speeds. The equation for drag has a squared term for velocity and a linear term for frontal area, so drag really goes up fast with speed and drag goes up proportional to frontal area ie. height. If you get lousy milage, one aspect to look at is the speed you drive. The higher you are and the faster you go, the more difference it makes.

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