*UPDATE*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 weighs in dry at approximately 8500 pounds. Loaded down I estimated the weight 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. The same code came up prior to the trip and I remove the EGR valve and cooler and clean them.
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.
If it's something I can check on my own that would be great before I took it to a dealer have a scanner hooked to it.

[Grit_dog]

16-1800rpms seems a bit low for towing that load at 65mph. Ime lugging Uses a bit more fuel than higher rpms towing. Can see it in the egts as they only go up with fuel usage.
I stuck brake would have burned itself out and youd smell it if it was hanging bad enough to knock you 3-4mpg I believe.
When I used to watch mileage on my trucks there would just sometimes be worse mileage seemingly inexplicably.
Since it sounds like everything is pretty normal w the truck, runner for a full tank or 2 unloaded and see if you get correspondingly bad mileage. If it's a real engine condition causing it, you'll get poor mileage empty too.
And get a tune for power, not mpg. Good tunes will squeeze out a little more mpgs in general, but ime you end up using the power which uses some fuel!

[1971duster340]

Did you change the fuel filter? The only time I've gotten fuel usage that's not normal or too few MPG was air leaking around the filter and getting into the fuel delivery system. Mine's an '05 LLY and 10-12mpg, doesn't seem to matter what I'm towing...TT, car hauler, enclosed trailer...24-27mpg @ 60-70mph, no load.

[73guna]

DirtyOil wrote:
like the post where one says he can smell the diff. between diesel trucks with and without catalytic converters... cats do little for diesel exhaust. quite a few naysayers... how many of you naysayers run with deletes and programmers? You'd be surprised what EFI live can do to a D-max for power and or mileage and still be safe. In the meantime I'll keep my mileage to myself after doing EGR and DEF deletes and programmer to my 2013 Ram CTD. Doing the DEF alone will pay for my system within 4-5 months ... not having to pay for DEF fluid anymore.

Dirty,
Ive been back and forth with myself on getting efi live.
Im well aware of the awesome power gains to be had with it however, from asking around on duramax forums it seems towing mpg's stay relatively the same.
Have you had gains with efi live and towing?

[73guna]

Ok, thanks to all those with the helpful replies.
I'll try to answer your questions.
1. Mileage was hand calculated and compared to my dash mpg, was within a tenth or two.
2.Havent noticed any more black smoke then usual.
3.I believe my rpms at 65mph is around 1600-1800.
4.A stuck brake crossed my mind, I never checked for heat on the hubs when I stopped but I did walk around the trailer for a visual check each time I stopped and didnt smell anything hot or burning brakes.
5.Defintely going to have the injector balance rates checked too.
6.Im guessing my trailer is 11' tall.
7.Not sure what my unload mpgs are lately because I hardly drive this truck anymore, just used to pull camper/haul things.

Im no stranger to figuring mpgs, Ive done it weekly for years on my daily drivers.
I know my truck well, this condition is not normal.

[73guna]

Hate to be blunt, but if you all want to b!tch and argue about someones mpg claims take it somewhere else before my thread gets deleted.

Now lets get back on track before I sick the mods on yawl.

[DirtyOil]

Me Again wrote:

carpetguy2 wrote:
I don't care what you guys say or think.
I know how to calculate my mpg
.And I tow in my mileage tune and had great success. My 40 ft trailer only weighs 12k loaded .
So maybe I know how to drive better than most of you I guess

like the post where one says he can smell the diff. between diesel trucks with and without catalytic converters... cats do little for diesel exhaust. quite a few naysayers... how many of you naysayers run with deletes and programmers? You'd be surprised what EFI live can do to a D-max for power and or mileage and still be safe. In the meantime I'll keep my mileage to myself after doing EGR and DEF deletes and programmer to my 2013 Ram CTD. Doing the DEF alone will pay for my system within 4-5 months ... not having to pay for DEF fluid anymore.

[Me_Again]

carpetguy2 wrote:
I don't care what you guys say or think.
I know how to calculate my mpg
.And I tow in my mileage tune and had great success. My 40 ft trailer only weighs 12k loaded .
So maybe I know how to drive better than most of you I guess

[Bionic_Man]

The brake dragging is an interesting idea, but I think if that happened you would end up smoking your wheel bearings and your tire. At least that is what happened when I had a single brake that was dragging - ended up overheating and blowing out the tire.

[NC_Hauler]

carpetguy2 wrote:
I don't care what you guys say or think.
I know how to calculate my mpg
.And I tow in my mileage tune and had great success. My 40 ft trailer only weighs 12k loaded .
So maybe I know how to drive better than most of you I guess

"MAYBE", and "I GUESS"..that's a lot of "iffy" data....Most are going from years and years of experience in towing...I've been towing for 41 years...so yeah, I "GUESS" "MAYBE" you can drive better than "MOST" of us:R....keep that truck.

[N-Trouble]

carpetguy2 wrote:
I don't care what you guys say or think.
I know how to calculate my mpg
.And I tow in my mileage tune and had great success. My 40 ft trailer only weighs 12k loaded .
So maybe I know how to drive better than most of you I guess

Better known as "internet mileage" LOL...

[NC_Hauler]

larry barnhart wrote:

NC Hauler wrote:

larry barnhart wrote:
I have been told a few times about getting 15 mpg towing bigger than our 35 ft alpenlite. Every guy had the 6 cylinder diesel engine. No matter what the engine would be it was a "really" answer from me.

chevman

4-6-8-10 cylinder....don't matter..I never heard of that kind of mileage towing a 40' 5er, no matter how many cylinders the engine had...When that truck dies, I'd have it stuffed and use it in the living room as a rug:B


Jin

same here but guys don't like to hear stuff sometimes. I believe in facts only. I was told by one of who I was telling about he has over 1200 ft in his cougar fifth. Makes the big MH folks jealous. WOW was all I could think as he is a smart man really.

chevman

:B

[Walaby]

With my diesel, best mileage is at 64MPH, running 1700 RPM. I bet if I get up to 65-70 it would drop alot. Now, mine is a Cummins, and in flat tow, on cruise, Im getting right about 11.5 mpg. I don't think that would drop to half or so at 70, but I don't run at that speed, because I have ST tires, and they will self destruct at 65.

As far as deletes etc go, a friend of mine has a Ford F250 diesel (2008). He did the DPF delete and a tune. He was getting 10 to 11, and now he's at 11-12, but more throttle responsiveness.

Granted, neither are Duramax's but it's a data point.

As far as 15MPG towing a 40', I'll call BS. Don't see that happening. Nothing short of me sitting in the right hand seat for a 1000 mile trip will convince me otherwise. Just my thoughts.

Mike

[Lantley]

carpetguy2 wrote:
I don't care what you guys say or think.
I know how to calculate my mpg
.And I tow in my mileage tune and had great success. My 40 ft trailer only weighs 12k loaded .
So maybe I know how to drive better than most of you I guess

Yea that must be it:S
You figured it out the rest of us are still learning. Maybe one day we'll get it figured out:?

[carpetguy2]

I don't care what you guys say or think.
I know how to calculate my mpg
.And I tow in my mileage tune and had great success. My 40 ft trailer only weighs 12k loaded .
So maybe I know how to drive better than most of you I guess

[larry_barnhart]

NC Hauler wrote:

larry barnhart wrote:
I have been told a few times about getting 15 mpg towing bigger than our 35 ft alpenlite. Every guy had the 6 cylinder diesel engine. No matter what the engine would be it was a "really" answer from me.

chevman

4-6-8-10 cylinder....don't matter..I never heard of that kind of mileage towing a 40' 5er, no matter how many cylinders the engine had...When that truck dies, I'd have it stuffed and use it in the living room as a rug:B


Jin

same here but guys don't like to hear stuff sometimes. I believe in facts only. I was told by one of who I was telling about he has over 1200 ft in his cougar fifth. Makes the big MH folks jealous. WOW was all I could think as he is a smart man really.

chevman