Well guys I just got my truck back after taking it to the dealer for horrible fuel mileage. 8.3 towing and 13 empty. The truck also has spells where it feels like it has no power at all when towing. GM actually said they felt this was pretty good and were not going to do a thing. As far as improving my mileage and curing the loss of power I need to run Stanadyne Junior through the fuel system. Because basically the Injectors are to sensitive for pump fuel. What a load of Shttp://www.dieselplace.com/forum/images/smilies/censored.gif !!
I have contacted GM to tell them how dissapointed I am with the LLY vs The LB7 performance and feel there is an issue with my truck. If they offer no resolution I saw a pretty nice "King Ranch" that would look pretty good pulling my trailer. http://www.dieselplace.com/forum/images/smilies/rant.gif http://www.dieselplace.com/forum/images/smilies/rant.gif

Do some real hard reseach on the 6.0 before you jump ship. Been there....done that. Have a year of my life wasted on that engine....

If you are getting 13 Hwy in a stock 3500 DRW, something is wrong.

Get a friend with a Tech II or a Predator to check your balance rates. Possibly a stuck injector. Watch your oil level carefully as well.

Now if you are getting 13 around town, that is normal. 8000lb pickups do not get good mileage in stop and go conditions. Doesn't matter what brand it is, or whether it is a LB7, LLY, or what.

As far as towing goes, there are too many variables to say what is good or bad. I got 11.5mpg on a 5000mi round trip at 17,000lb combined, which is normal.

You didn't mention how fast on freeway. 80 mph @ 13 mpg isn't so unreasonable. At 67 mph, it would be.

Speed was held between 65~68 MPH. I had the rig weighed at a cat scale. 20,500lbs total weight

Depending on how many mountains, headwinds, and frontal area of the trailer, it might be normal, but it does sound low to me.

If it's any condolence, a gasser would be lucky to get 6mpg at 20.5k. At 13k, my gasser got 7.

Well guys I just got my truck back after taking it to the dealer for horrible fuel mileage. 8.3 towing and 13 empty. The truck also has spells where it feels like it has no power at all when towing. GM actually said they felt this was pretty good and were not going to do a thing. As far as improving my mileage and curing the loss of power I need to run Stanadyne Junior through the fuel system. Because basically the Injectors are to sensitive for pump fuel. What a load of Shttp://www.dieselplace.com/forum/images/smilies/censored.gif !!
I have contacted GM to tell them how dissapointed I am with the LLY vs The LB7 performance and feel there is an issue with my truck. If they offer no resolution I saw a pretty nice "King Ranch" that would look pretty good pulling my trailer. http://www.dieselplace.com/forum/images/smilies/rant.gif http://www.dieselplace.com/forum/images/smilies/rant.gif
grass is always greener on the other side. I have a 6.0 7.3 a 6.6lly.... the lly is the only one that has not stranded me. the Late 2004 6.0 blew off the intercooler line just last week and put a nice bubble in the hood.

Howard

How many miles are on the truck? My milage seemed to get better after 3K. I was getting about 13 mpg at first and now im getting 16 in the same conditions. Mine has 4k on it now. Just a thought!

miles are about 7k

I'm not sure if it was change from winter fuel to summer and mileage or just the mileage but my truck made a night and day change between 9000 and 9500 miles about 2.5-3 MPG better it was consistent 12-14 mixed before not 15-17 mixed city and highway.