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Discussion Starter #1
Hello guys Ive got an 07 LBZ 2500 4x4 totally stock. While towing a 10,000 lb load I normally get 10-12mpg depending on speed etc. On my last couple trips I'm only getting 5-7mpg. Right before this occurred I changed the fuel filter but cant see why that would cause the increase in mileage. Also have cleaned the MAF sensor and changed the air filter. When not towing the truck gets 17-18 on the highway and about 13-14 around town. Any ideas guys?
 

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Trailer wheel bearings going bad or brakes dragging?
 

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Moving to towing-- this is not 911
 

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I would look at your trailer as well.
 

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you should take into account wind. whether it is cross or head winds.
amount of hills. tire pressures.
another thing is the quality of fuel.
have you tried lucas fuel treatment?
 

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Discussion Starter #6
My first thought was the trailer but I learned that wasn't the problem after pulling a similar trailer and got about the same fuel mileage. Secondly the terrain is mostly flat, Ive used at least 10 tanks of fuel from different places with similar results. I use sea foam and that helped a little but not much. The weather is warmer when I lost the mileage but not by a huge amount maybe 15-20 degrees. Tire pressure is good on the truck and trailer.
 
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