Calling Duramax owners 1st trip with camper bad fuel mileage

[73guna]

I have a 2007 crew cab Duramax LBZ 4 wheel drive.
We recently got back from our first camping trip with our new Wildwood 31qbts. The trailer ways in dry at approximately 8500 pounds. Loaded down I estimated the wait to be right close to 10,000 pounds.
My mileage on the trip was anywhere from 6.5 to 7.5 miles per gallon.
Fresh oil change with synthetic right before trip, tires aired up to 80 pounds, new fuel filter.
Cruise was set between 65 and 70 miles per hour on the flat in the hills I pedaled it. We had a pretty good crosswind all the way down to our campsite and a little ways back. Once the wind stopped I check my fuel mileage again and it was still within the same range.
On the trip I did have a check engine light come on which was p0401 which indicates low flow in the EGR valve.
Now, before I go on to the Duramax forums and have all the Young Guns tell me to delete the EGR and step up to EFI live programming I would like to get to the bottom of this and figure out what is causing my poor fuel economy.
Just wondering if anyone else has ever dealt with poor fuel economy and what you did to resolve the issue.

[jalichty]

We have a 2012 GMC with which we pull a Jayco HT 26.5 RLS and a 19' Crestliner and get about 12 mpg on all of our trips to the lake to fish and relax, about 150 miles away up over a pass and then back down to the lake, and reverse on the way back. Took our FW only on a 3,800 trip two springs ago and got 12 mpg, hand-measured for the whole trip. You might have and injector problem because I even got that mileage with my 2003 GMC. Not so good with the 2011 Ram diesel that I had for about nine months.

[killerbee]

Suggest override to 5th gear, and run the speed that keeps you between 1800-1900 rpm. Do not use CC. If you want to use D, we have TCM custom tuning that will prevent 6th gear lugging, and 5-6-5 hunting while in CC.

These parameters should help the efficiency at higher altitudes particularly.

[Roger10378]

What is the height of your trailer. Height is a bigger part of fuel economy than weight. LBZ should get better than that even at that speed, but slowing down would help. My LMM gets 11 mpg or a little better with a 13 ft. high trailer and a little over 12,000 lbs. loaded. I try to stay under 65 but not always successful. You need to figure out what is causing the EGR problem as it could affect mileage.

[donn0128]

Must be real important, posted three times now.

[coolmom42]

That's about right for the weight you are towing and at that speed.

Slow down. If you are running trailer tires, that's above their speed rating.

[janstey]

Speed is your enemy, drive 55-60 for best MPG.