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is this mpg possible???????

S

sidelined

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Northeast, MS
It appears that I ran about 240 miles on a tank. With a 34 gallon tank that is around 7 mpg! Now I'm hoping I was robbed after all!:mad2:
 
Towing or empty, if towing what were you towing, 7 mpg empty for sure is wrong; 7 maybe if towing something REALLY heavy or REALLY tall with a lot of wind drag, but even with 4:10s that is off the mark.
 
What size tires on there? 245/65?

How was everything performing? Black smoke? If so, how much? Did you just recently purchase the truck... ie: are you sure there isn't a performance chip in there? Although, it would have to be a bad program to cause that type of MPG.

If everything seems to be running A-OK, try again before you worry. Make sure you fill up exactly the same way each time.
 
DennisG01 said:
What size tires on there? 245/65?

How was everything performing? Black smoke? If so, how much? Did you just recently purchase the truck... ie: are you sure there isn't a performance chip in there? Although, it would have to be a bad program to cause that type of MPG.

If everything seems to be running A-OK, try again before you worry. Make sure you fill up exactly the same way each time.
Click to expand...

Had the truck a few weeks. Everything else is normal. No smoke other than very little at a cold start up. Original size tires, cant recall right off. Not sure about a chip. Im gonna fill up today and start over. I'll keep yall posted.
 
i had 14mpg as worse with my suburban...something must be really wrong... or someone is helping themself to your diesel!
 
do you have any leaks? my truck got 7 mpg once because one of my fuel return lines on the passenger side fell off so all the fuel not being used by three injectors was all being dumped on the ground
 
Once the pump clicks off I can always reliably (with some patience) add another 10 litres to top it off.

Once full, it takes about 200 km for the needle to even start to move off of being pegged above full.

GM fuel gauges are like that.

It seems as though this may be have been your first fill and you may not really have a good grasp of calculating fuel mileage.

Here's how.

1. Fill the tank up yourself as described above, don't let a gas jockey do it, he won't be as patient as you (should be), right to the top of the filler tube,
2. record mileage,
3. drive, keep in mind the optimum RPM for this engine is ~1800, and in a 3500 DRW stop and go city driving will kill you.
4. fill again as described above, recording miles and gallons, litres or whatever, and divide miles travelled by gallons burned.

This will then be an accurate test, and then report back, but be advised that driving (without regard to RPM, accelerating with gusto, etc.) are the major contributors to excessive fuel consumption.
 
The worst fuel economy I have ever had on my truck is 11.2MPG. That was pulling my RV threw the hill country here in Texas.

It is my truck in the sig and I have 4.10 rear end.
 
sidelined said:
no visible leaks.
Click to expand...

As someone else stated check injector & IP return lines if you have the braided return lines you can't see a break in rubber hose underneath them, they get hard & crack and ones near turbo are the worst as they are subjected to most heat and if leaking splash on the turbo down pipe residue burns off and doesn't really puddle unless really observant and you don't know you have a leak.

Did the previous owner say anything how old your current injectors are?
 
chickenhunterbob said:
Once the pump clicks off I can always reliably (with some patience) add another 10 litres to top it off.

Once full, it takes about 200 km for the needle to even start to move off of being pegged above full.

GM fuel gauges are like that.

It seems as though this may be have been your first fill and you may not really have a good grasp of calculating fuel mileage.

Here's how.

1. Fill the tank up yourself as described above, don't let a gas jockey do it, he won't be as patient as you (should be), right to the top of the filler tube,
2. record mileage,
3. drive, keep in mind the optimum RPM for this engine is ~1800, and in a 3500 DRW stop and go city driving will kill you.
4. fill again as described above, recording miles and gallons, litres or whatever, and divide miles travelled by gallons burned.

This will then be an accurate test, and then report back, but be advised that driving (without regard to RPM, accelerating with gusto, etc.) are the major contributors to excessive fuel consumption.
Click to expand...

Not sure how else to calculate fuel mileage. 240 miles divided by 34 gallons = 7.058. The tank was full and ran it out. But in any case, its full again and we'll see what happens. As for 1800 rpm, thats gonna be hard to do. I understand the gear ratio is terribly low. But I just dont believe this thing should get as bad as a loaded semi!
 
sidelined said:
I could live with that.
Click to expand...

That is the worst I have ever gotten in my truck. The best is around 19.5.

Man, the only way I know of to get that bad of fuel economy would be a boat anchor tied to the rear bumper or fuel leak(line or hole in tank). Maybe someone stole some fuel out of your tank? I hope not on all the reasons above.

What exhaust you running on your truck?
 
exhaust is stock, as is everything else to my knowledge except the added fuel tank. I would be shocked if it was stolen, but anything is possible. Its full again, so we'll see what happens around wednesday. In the mean time Im gonna check all the lines and everything I possibly can. I have been trying to figure out how they set up the aux tank to feed the system. It appears that a flip of the switch fills the factory tank from the aux tank. Which seems to me to be a good set up.

As for the previous owner, he only had the truck around 6 months and didnt drive it alot. He only used it to move a fifth wheel around locally that he was living in after his house burned. He was the second owner, the first used it to pull his fifth wheel also, he was a contract worker so Im guessing he traveled all over the country. It had 99,567 original miles on it when I got it a few weeks ago. It runs incredibly smooth imo. I dont know if IP, injectors or anything else have ever been changed. I plan to start replacing some of these common problem parts soon, but ran into this problem this week and have to get that outta the way first.
 
My truck has 186,000 miles on original IP and injectors. It still runs like a top.

If you had or have a fuel leek you would know. Every time you are within a 50 foot radius of your truck you would smell diesel.

Without a ton of pictures or being next to your truck I would have no clue on your in bed fuel tank.

Is it possible somehow some of your fuel is being sucked into the tank you are not using from the tank that you are?
 
sidelined said:
Not sure how else to calculate fuel mileage. 240 miles divided by 34 gallons = 7.058. The tank was full and ran it out. But in any case, its full again and we'll see what happens. As for 1800 rpm, thats gonna be hard to do. I understand the gear ratio is terribly low. But I just dont believe this thing should get as bad as a loaded semi!
Click to expand...

Suit yourself, you can ignore me if you wish, I explained how to fill your tank, how your gauge is quirky, but I get 24 MPG with highs of 26 highway, and an annual average of 21 for all combined driving.

240 miles divided by X gallons only matters if you filled the tank to the exact same level, both times.

Believe it or not, but has been proven that lowest fuel consumption is at 1800 RPM. You can drive at whatever RPM suits you, just don't bitch about your fuel mileage, because now you know the reason why.
 
Listen to ChickenhunterBob, it takes me about five to eight minutes to get the fuel filled all the way to the neck at fill ups, The pump clicks off and I can add another 5 to seven gallons before the fuel is at the top of the neck. It is the only real way to accurately measure fuel mileage, by having the fuel at the top of the neck.

I have a lot of things going on and run at 80 to 85 at 2700 to 3100 rpm a lot and still average about 13 mpg with my truck. Something is wrong, may want to lose the soot trap or you may have a collapsed exhaust, either way it is a good place to start.
 
I think a locking fuel cap is what you need, you had posted in another thread how the gauge read full at night and then in the morning it was 1/4.
 
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