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Discussion Starter #1
New to the forum and to diesels so bear with me until I get the hang of this.

What MPG can I expect from my 04' (bone stock) crew, 2WD, LT, 6sp AT. I keep hearing these tales of 18-20 MPG avg, but I am about 4 MPG short at 14.5 empty. I have been running the Power Service supplement at 3 points increase in cetane if that matters. I have changed the fuel filter, had all 8 injectors replaced and am pondering a programmer.

Also, my fuel management system shows my getting 18-20mpg, but as you have read above it ain't gettin' it. How accurate are yours when compared to checking at the pump? The truck runs smooth (now that it has new injectors) and seems to pull ok, but I have noticed my turbo does not "sing" like most stock Dmx's I have heard. Is it possible the turbo is not spooling just right? I have read a little on it being a variable computer controlled turbo, but would a faulty turbo (or beginnings of a faulty turbo) show a DTC?

Any help would be appreciated!
 

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I personally think it all depends on the truck. I get around 15.5 to 17 around town...and 18.5 to 20 highway. But I am not really hard on the throttle...and highway I don't go over 70MPH. I run Stanadyne conditioner in mine. I used to get better gas mileage...but I put one size bigger tires on..and an aftermarket exhaust...that lowered it a bit. And as far as my fuel management system (DIC) goes...it says I'm getting 16.9 ALL the time. It never changed in 8,415 miles. So it's crap. And Welcome to the Forum!
 

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14.5 around town right? because if thats what your getting on highway, your kinda short.
 

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i get about 15.5 combine with my edge at 100 horse
 

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welcome to the forum..good question and you'll get different anwsers from every body and i have found out it depends on the Throttle Position Sensor more then anything..on my stock 06 LBZ i was getting 13 to 14 aroung town and 18 on the highway but since i did a exhaust and programmer it jumped by 3 to 4mpgs straight across,if i tow it drops down to 12 and 14mpg really quick..
 

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New to the forum and to diesels so bear with me until I get the hang of this.

What MPG can I expect from my 04' (bone stock) crew, 2WD, LT, 6sp AT. I keep hearing these tales of 18-20 MPG avg, but I am about 4 MPG short at 14.5 empty. I have been running the Power Service supplement at 3 points increase in cetane if that matters. I have changed the fuel filter, had all 8 injectors replaced and am pondering a programmer.

Also, my fuel management system shows my getting 18-20mpg, but as you have read above it ain't gettin' it. How accurate are yours when compared to checking at the pump? The truck runs smooth (now that it has new injectors) and seems to pull ok, but I have noticed my turbo does not "sing" like most stock Dmx's I have heard. Is it possible the turbo is not spooling just right? I have read a little on it being a variable computer controlled turbo, but would a faulty turbo (or beginnings of a faulty turbo) show a DTC?

Any help would be appreciated!
well, those tales of 18-20 mpg isn't a tale if you can drive on the highway. I have seen 21 mpg with mine when it had the stock tires on it. Most of the tales are just that though because some people don't hand calculate their mileage. They go by what their computer tells them. After adding a programmer, it throws the computer off by a good bit. You can gain a couple of mpg by using a programmer, but your computer will be off some (mine is usually off 5-9 mpg depending on the programming I use). I personally get about 15-16 around town and 17-19 on the highway even with bigger tires....my speedo is corrected for the bigger tires and I always hand calculate the mileage..(my DIC says I get 25-28)

Also, what engine do you have in your truck (LB7 or LLY)? Check the 8th digit of the VIN...if it is a 1=LB7 and 2=LLY. The LLYs on average got less MPG than the first generation LB7 too. Also, the LLY has the VVT (Variable Vane Turbo) where as the LB7 has a fixed vane turbo.
 

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Discussion Starter #7 (Edited)
I have the LB7 (8th digit is a 1). So this has the fixed vane rather than the VVT? It appears I am in for a wad of info in the next few months huh? Thanks for the help guys!

I just poured in some "Killem" in the tank upon reccomendation from a fellow diesel owner in case I had some funk built up in the tank. He said this muggy climate we live in causes some issues with buildup in fuel. I am doing the 2 "shock" treatments in hopes this may help with the mileage issue should it be one of the potential causes.

Thanks for all of the help!
 

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Also, you will want to change the fuel filter at least once after you run the biocide in the tank. Believe it or not, you should gain a few MPG by changing the fuel filter.
 

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I have an 06 GMC and before my first oil change was getting as high as 21.3 MPG on the road at around 75MPH. Now the most I just got back from a trip and the best I got was 18.5 MPG. I am wondering if the dealer put the wrong weight oil in my truck.......:confused::confused:
 

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Remember how much mileage you have on your truck makes a diff. When i 1st got my truck i was at about 13.5MPG @ about 70MPH. Now im at about 17 at about 45,000KM before my lift. Expect top mileage at about 80,000k
 

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My mileage is 56K and I live in East TX. No altitude to worry about here just a TON of humidity and heat. I just got a decent figure on the MPG after the injector replacements and I am getting roughly 15.7 MPG empty and about 14 when pulling my race car once a week on a 60 mile round trip. This of course is figuring a weeks worth of driving empty AND pulling the car on the weekend. As soon as I run this tank out I will replace the filter and post what I discovered.

I have made a few fellas upset around here by pointing out the inaccuracy of the display MPG. They are slowly rolling in with stories of 15-16 MPG with one 18 MPG. They had never checked it at the pump!
 

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Olddirtrider -- oil weight will not affect your friction loading except at cold start. With the ambient temperatures in August, I doubt that the oil viscosity would differ much during cold start. If you calculate your mileage and fill the fuel all the way up the filler, you should find similar mileage for the same conditions on the 06MY engine. Was it unloaded, even road, constant 75 mph? Head winds, hills (elevation from one point to the other is a contant increase or decrease if going on a long trip). Might want to check your air filter to see if it is clean -- the restriction can affect you a little bit. The fuel cetane could be marginal on your last batch of fuel... even the same station can get two different batches of fuel. lots of little things. Good luck with your quest.
 

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Well what I think really happened is that the dealer up dated the software on the 10,000 mile service. I have consistently gotten over 20 with no load up hill down hill for over a year till I took it in for service. So it has to be something related to the trip to the dealer!

Thanks for the message!

Alan
 
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