is this mpg possible???????

[GM Guy]

I fill my tank the same way chickenhunterbob does. and on a chassis cab with improperly laid fill hose, it is a 15 minute fillup, so I am dedicated! it is the only way to know for sure how good or bad your mpgs are, and the only way I can prove the superiority of manual 2wd trucks concerning fuel economy!

I got 4.10s, and can get 20 mpg, the key is gentle driving, and low RPMs.

 

[great white]

7 mpg empty is low brother!

My 98 has new optimizer (new, not a take out military), 4:10's, 4l80E, and 4x4. My tires are one size over BFG's (waiting for them to wear out to change them- $$$$$!)

Towing my 8500-ish lb 9 foot high x 8 foot wide TT netted no worse than 8-10 mpg.

Empty day to day driving (around town) nets around 13-14 mpg. Highway will return around 14-15 mpg. I hit a high once of 17.5 on highway empty running, but I'm pretty sure that was an error in the pump reading as I've never been able to duplicate it.

Remember that that diesel is inside the engine bay of a truck. IOW, more than what's going on under the hood can cause poor fuel mileage.

Some things to check for: brake drag (ie siezed calipers, etc), partially stuck on emergency brake, poor alignment (usually accompanied by abnormal tire wear), tire inflationn values, and finally - driving style.

Engine stuff like worn injectors, worn engine, clogged air filters, etc, will effect mileage but you have to remember the vehicle is a system and you must trouble shoot it as such.

If you have an old truck, it's very likely you could have a combination of things going on. For example; a dragging e-brake cable combined with worn injectors and a worn ip can all conspire to kick you mpg in the butt. Chuck in some low tire pressures and a tank of winter diesel and it can drop throught hte floor and hit an all time low and take the wind right out of you sails....

7 mpg sure does sound like you have a couple things going on at the same time. This is all assuming your math is good.....

Good luck hunting it down, i hope you find it. 7 MPG is pretty disheartining in the days of $1.36 a liter diesel........

Cheers

 

[chefmike]

ANother thought about that 34 gallon tank: it will not hold 34 gallons if it is imploded. My 42 gallon tank would only hold 30 gallons after it imploded. PO had put on a locking GAS cap (no vent) and was running with a dead IP. Tank sucked in big time and stayed there. When it happened it bent the fuel sender, changing the guage readings.

Just a thought.

My wife got siphoned at work (she works nights). So that is also a strong possibility.

 

[bison]

Now i don't know where you fill up.?
I fill up from my farm bulk tank and don't know how much i actually put in a tank.
The 98 in my sig ran out of fuel with only 150 km on a "full" tank when i first got it.
Happened to be a collapsed tank.:WTF:
Since then i leave the fill cap loose.

 

[dangerousdave]

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.

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.

:iagree: Start with the easy stuff; air filter, locking filler cap, clogged soot trap (sometimes mistakenly called a catalitic converter). Does the turbo spin at all?

An Anomaly; if the intake snorkel is still OEM, it could have a rats nest or something in it...
Reminds me of when a flock of pigeons landed in front of me on a desert highway; intake blockage, radiator blockage, :hihi:

See my sig; Worst we ever got was when we first bought it; it was all OEM; intake snorkle, plugged soot trap, mangled down pipe(coming out of the turbo), and failing PMD, loaded with people and luggage in the California hills. That was 14.5mpg IIRC.

Welcome aboard.

 

[tanman_2006]

I fill my tank the same way chickenhunterbob does. and on a chassis cab with improperly laid fill hose, it is a 15 minute fillup, so I am dedicated! it is the only way to know for sure how good or bad your mpgs are, and the only way I can prove the superiority of manual 2wd trucks concerning fuel economy!

I got 4.10s, and can get 20 mpg, the key is gentle driving, and low RPMs.

My 93 4x4 dually 5speed has gotten 19 cruising 75mph with 4.10's. I wish i could keep it but i cant afford to keep it since it hasn't ran enough to earn its keep. The filler cap on that truck is set perfect flat with the side of the bed and welded in so it is a PITA to fill.

 

[JiFaire]

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.

Miles per American Gallon, or Miles per Canadian Gallon, CHB?

 

[GM Guy]

My 93 4x4 dually 5speed has gotten 19 cruising 75mph with 4.10's. I wish i could keep it but i cant afford to keep it since it hasn't ran enough to earn its keep. The filler cap on that truck is set perfect flat with the side of the bed and welded in so it is a PITA to fill.

white? check
five speed MANual? check
duals: check
mechanical injection: check!
2wd: negatory.

four out of five is close enough for interest. what do you have to have out of her?

 

[chickenhunterbob]

Miles per American Gallon, or Miles per Canadian Gallon, CHB?

Imperial gallons, since I live in Canada.

 

[gcxcountrystar1]

I live on the boarder of missouri and illinois. i have notice that when i fill up in missouri it last longer than if i fill up in illinois. i also get better gas mileage if i fill up at a truck stop then if i fill up at a small gas station that may not get as much diesel customers.

 

[great white]

Imperial gallons, since I live in Canada.

Then your mpg is not quite comparable to what the boys south of the border are using.

1 Imp gallon = 1.2 USG

So those MPG numbers are going to be a bit lower when recalculated.

Since you've got .2 USG more, a simple calculation reduction of .2 in the MPG figures works out to:

25 Imp MPG = 20 US MPG

20 = 16

16 = 12.8

That's if you want to compare appples to apples for our southern brethern....those numbers are a lot closer to what most claim from thier 6.5's.

 

[sidelined]

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.

At what point in my post did I imply that I would ignore you? I simply said that was the only way I knew to do the math. This is exactly the kind of response that keeps new guys like me from asking for input on a site like this. You are the first person I have came across on here with such an arrogant attitude. According to you, Im btichin because i was shocked at how horrible the mpg was just because I came on here and asked a few questions. And as for filling the tank to the exact same level "both" times, it was the first fill up. Wasnt even trying to check it until it ran out and surprised me and then I ran the numbers. Now maybe I should have waited about posting and figured this out on my own before forcing you to waste your valuable time and having to explain something to someone so beneath you as me, but if we all did that, there wouldnt be much use for a forum. I applaude your mpg, that is awesome mileage. But if coming here to ask a few questions is considered bitchin I will be glad to move along.

To everyone else that knows how to talk to people without talking down to them , thank you for your input. It is very much appreciated.

 

[sidelined]

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.

Yeah, I saw friday what you mean by it taking forever to fill up. Guess I'll start just filling the aux tank and let it fill the factory tank. Much quicker.

 

[JiFaire]

Hang in there, sidelined.. it gets better.

There are a few pretty important nuggets in the responses you have had so far:

-- measure only with the amount of fuel you have personally put through the truck... don't try to guess at tank size

-- this process takes quite a bit of time, because every fill comes up at a different level, unless you want to spend 20 minutes trickling it in. Take the average over a number of fill-ups, and you'll get closer and closer to the actual numbers.
(they don't have to be complete empty-to-full fill-ups, either... fill it every day for a week, take the total amount miles you drove, divide by the total amount of fuel you put in, and you'll be pretty accurate.

-- tank volume is anybody's guess. There are 3 different tanks that go on these things, and so the volume can be different right from the factory. Also, the point about collapsed tanks (suction) is very valid.

-- leaks stink... you will definitely smell it if you have a diesel leak.

-- get a locking cap. The way fuel prices are now, somebody can grab $20 worth of fuel out of your tank in under a minute, with an electric pump. Make sure the cap is for diesel, so you don't have the vacuum issue described above.

 

[sidelined]

Thanks, as you said everyone had valuable things to add. And I pay attention whether someone thinks I do or not. Im not here to offend anyone at all, just threw something out there because I was surprised by it. But oh well, I trickle filled the tank friday so we'll see what this week holds for me.

 

[Gunner0812]

Hope you get the problem fixed!

 

[sidelined]

Thanks, we'll get it figured out, just gotta start the elimination process.

Hope you get the problem fixed!

 

[Paveltolz]

I've been thinking about this thread off and on since you first mentioned it in your upgrade thread.
Putting myself in your situation, if my truck gave me a low MPG number that seemed way out of what should be norm, my mind would spin uncontrollably. So much so that I would fill up after a couple of days to get an idea how things were going. Yes, the number wouldn't be accurate from a whole tank MPG view but it would give an idea of what may be happening/have happened: 1) an odd ball reading, 2) ripped off, or 3)there is a mechanical/electronic issue. The MPGs should be much higher if it wasn't mechanical (meaning you got an odd reading or ripped off) or back down at 7mpg mechanical/electronic issues to be ascertained). I’m in the hopes that you got a bad reading/tank full. If it is an issue with the truck, may the solution present itself without too much trouble or $$$ spent.

 

[sidelined]

Thanks man, judging by last week, we should know around wed or thurs this week. :hihi:

 

[GM Guy]

By trickle filled, I take it the bed mounted auxillary tank is plumbed right into the vent line of the OEM tank, and it is just gravity fed, rather than pumped, and you just filled the bed tank, opened your valve, and watched inside your OEM neck until you saw fuel, correct? If so, that sounds like a great way to accurately fill the tank.

Just fill the bed tank up after you fill the truck tank, (if the pocketbook can handle it, ***** fuel prices these days..those 2 diesel wabbits for 950 bucks are looking cooler every day.. anyways, back on track. ) and then repeat the process next fillup. that way, you got every fuel holding vessel on the truck completely full, and then just do the trip meter miles divided by the total gallons.

also, what size tires are you running? GMT400 DRW trucks, pickup or chassis cab, both have the LT225/75R16D tires, so if you got anything else, your odometer is inaccurate.

good luck, hopefully you arent getting robbed, anything these days is so expensive, crooks will grab anything. May we all hope and pray they think you got a gasser and pump into their gas vehicle. surpise time: instant Karma! gasser no likey diesel!