I brought my truck to the dealership last Monday with complaints of terrible fuel mileage and hard to start. They decided to reprogram the computer to update the EGR. They called me after a couple days and said it was finished. I asked the advisor if they had checked to see if the EGR was bad, and he said they had and it was OK. I also had it in there for the steering shaft rattle and front body mount popping. Of course neither of those issues were fixed. I went down on Thursday morning and started it before they could, and of course it took a while to start. I finally got a mechanic on the job that seemed like he knew what he was doing. Friday he called me and told me the EGR was bad and that the inside of the intake was loaded with soot. He cleaned it up and got everything back together. I also had a fuel leak somewhere, and it was found under the fuel filter at the water accumilator.

So now I have had the truck back since Friday and I have put about 100 miles on it. I have yet to break 11 mpg in town. It seems to get just over 11 when I get out on the freeway. When I stop and idle for about two minutes, it will actually drop almost two miles per gallon just idleing. On a trip last weekend before I brought it in, it used 46 gallons of fuel to go almost 400 miles towing an 1800 lb enclosed trailer. The clutch fan ran almost as much as my LLY did, and I noticed the trans got a little hotter than usual. My EGTs would sit at 1200 for miles on small inclines and easily hit 1400 at times. I have towed my 32 foot fifth wheel with this truck and got better mileage.

Are they any other areas of the truck I should have the dealership look at? Is there a possiblility the reprogram was installed incorrectly? I have been running stock program and 285 tires for the last two weeks just to see if there was any differance in performance or gas mileage. Frustated in PHX.

How long have you ran that fuel filter & air filter? Is it at all possible you got a bad tank of fuel? Did you fill up at a heavily used station, did you notice if a tanker was there recently to refill the station, it's been mentioned that when a station gets refilled that stirs up the sediment in the bottom of the stations tanks.

I checked my records and only have about 7k on the fuel filter. I am changing the fuel filter tomorrow just to be safe. I also changed out the oil today and put on a new trans filter. The stations here in the Phx area get used quite often, but I mostly fill up at two different stations. I have never had any problems out of them, or had water in the fuel. I am going to change out my air filter, I have 23k on it. I haven't decided if I want to use a factory filter again or switch to an aftermarket filter that will fit in my original box. Wednesday I will be putting on about 75 highway miles and see if it does any better.

Are you in the throttle heavy all the time? I run my LBZ hard and i get 15-16 mpg consistantly, 14 mpg towing my dump trailer with 7-8k lbs. I used to get 18-19 around town but it dropped with the 265's and i have been driving it harder. I tend to idle alot with the a/c on too. This is all hand calculated. The air filter will make a big difference too, i didnt lose alot of fuel milage but the power had dropped. I am sticking with the stock filter myself and the air box is cut.

I have been pretty easy on the throttle lately. I picked up some paperwork today from the dealership that is supposed to monitor my mileage readings. They want me to keep track of hours, mileage, and fuel used. I filled up yesterday and so far I am getting 11 mpg hand calculated. David

If you tear down any LBZ/LLY with an EGR, you'll find all kinds of junk in the intake. That doesn't make the valve bad, it just gives you reasons to block it!

I dont get more then 14mpg empty w/my lbz, 6.5 got the same milage doing the same route

The EGR was not in working order from what the mechanic told me. I was getting around 14-15 empty in town before I started having issues last weekend. On the highway, I could sometimes pull almost 19 mpg. I have a 450 mile trip this weekend towing about 1600 lbs one way and then 2800 on the way back.