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Discussion Starter #1
i have a 2006 gmc lly thats getting piss poor milage on hyw when empty but loaded it gets better what can i do too change this so i dont have too be loaded all the time
 

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Discussion Starter #3
sorry its got cold air 4 inch ext bully dog tuner after market tranny dont know what was done too tranny 33inch tires no lift i have about 145000 k on it and i have done both still dont know what too say
 

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'Ol Builder guy
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My guess would be be the tires. Oversize tires, especially those with knobby off road tread can take you down 1-2 MPG no problem.

All I did was switch to a mild off road tread on a stock size 265 and I lost about 1/2MPG.

The tuner could also be contributing. Take the tuner off for a few tankfulls and drive it the way you normally do and see if that increases fuel economy.

Check to make sure your tires are inflated properly.
 

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Terra AT type tires, Could there be something pluging up unless it has a load?
 

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We need more info. 2500 or 3500, SRW or DRW? How fast do you drive empty and how fast do you drive when loaded? How much weight are you calling loaded?

What are the fuel mileage numbers you get empty and loaded? Are you going off the dash reading for mileage numbers or are you doing the math at every tank fill?

I'm running my truck, a 2500 ECSB SRW LBZ. Empty on the highway I can get 22+ MPG when keeping my speed under 70mph. If I go over 70mph the mileage drops drastically.

Loaded with 6-7,000 lbs (a car ona trailor) I can get 16-17 mpg at the same speeds, again if I go over 70 mpg it goes to *****.

Loaded with 13,000-14,000 lbs I can get 12-14 mpg depending on terrain, speed, etc.
 
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Discussion Starter #7
mine is a 2500HD i get about 14mpg empty doing around 115k rpm is at 1600. load with car on a trailor and a slip tank full 450L i get about 22mpg and thats doin 115k over the same road all hyw
 

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Discussion Starter #8
i did buy the truck used with 65000k it look like it had a welder in the back at one time it runs strong i think theres more done to it that i dont know about
 

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Discussion Starter #9
im also wondering if my injectors are working better when the motor runs warmer loaded do anyone think i might have too change them if so too what stock or bigger?
 

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CRAZY CANUCK
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i cant see how your getting 22 with a load, im not even getting 20 empty, pulling a boat i get 17..... thats just a little boat!!!!!!! so i think something is a little fishy here
 

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when was the last time the fuel filter changed that may help what level is the bully dog on
 

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My guess is that it's something in the BD tuner. Something to do with the boost and PW would be my guess. The tables for fuel and air could be hitting the sweet spot for fuel economy with a little more throttle position do to the load as opposed to no load.

Other than that you got me stumped!!
 

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I get 17 mpg with a 380 hp to the wheels averaging between 70-75 so I'm not to sure something is f***ed up
 
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