So I made my trip down to myrtle beach for bike week and the reason I bought this truck was to haul our trailer 30ft. enclosed dual axel. We did not have that much weight in it only 4 street bikes, 3 four wheelers, and one dirt bike and lugage and gear. So I was figuring it out that we were getting anywhere from 8 to 12 mpg hauling, even though my gauge on the ceiling said 15mpg. We were doing anywhere from 75 to 90mph. So my question is this normal for that load. And BTW I just had the computer reflashed at the dealer for bad mileage and white smoke. I have a quadzilla mileage box on it now. Could the box be screwing up my computer again. Should I take it back to the dealer and have them re-flash the computer again. Please help on this situation.

Thanks
Nick

 

Seriously?

A 30' trailer with 8 bikes,luggage and gear,doing 75-90mph and you're complaining about mileage?

Speed is always going to be the biggest killer of mileage. Towing a big brick at those speeds and you see what happened.

Wind drag increases exponentially the faster you drive. There is something like 4x the wind drag at 60 than there is at 50.

The O/H is never accurate as is,adding a programmer just makes it more un-accurate.

 

i would not complain about that mileage with that load pretty good if you ask me. I went to bike week too pulling 6x12 dual axle with to bikes. i got 12-15 doing the same 65-90 mph.

 

My 06 will average 13.5, best ive got is just under 16, but right off the batt, I go 60 to 65 thats it, anything above that and the mileage drops off pretty quick, TT 30 ft about 8000 lbs. keep it below 2000 rpm and keep your speed down and your mileage should improve.

 

I got 16.1 MPG hand calc'd towing a 10k brick the length of the California central valley at 63 MPH on cruise, but with a 40 or so MPH tailwind. I then got 12.2 MPG going back and forth over the Grapevine and plodding along on the LA freeways. Empty, with about an 80/20 split between freeway and rural road driving, I get 17-18 MPG as a reference.

I knew it was good going down the valley as I was generally only making about 7 PSI of boost in OD at 1600 RPM.

Slow down, you'll be better off on a number of fronts.

 

When you tow w/ your 35's do you use tow haul mode all the time?

 

When I tow my 6900 LB empty toy hauler, load a few toys and haul at 5/6K ft elevations I am pleased to get anythng over 10 MPG. Mind you I don't keep my foot buried to keep it at 80 either, 65 works fine. A gasser would be lucky to get 7/8

 

I just got back from a 2600-mile family vacation with the 26ft t/t (about 7k) from the Seattle area around Idaho, Montana & Oregon doing ~65 and averaged 12.1 mpg. The lowest tank was about 9.5 climbing from the Columbia gorge into a headwind. The best tank was just over 13 coming up I-5.
That was still $1100 in diesel.

 

I would say that you did very well for mileage. When I pulled my 27 foot V-nose, I get about 10-11 average. But I don't normally go over 65 MPH. 75-90 MPH is going to kill your fuel mileage.

 

Yes, I find that the non-tow-haul mode seems much more willing to unlock the TC. When in tow haul I just mash on-off the throttle to kick it down to 3rd and it will hold that gear as long as the load stays up on the engine. BTW, I've got a BD valve body and a double deep pan in an otherwise stock transmission.

The trip in question was a one-off towing a school's trailer. Typically, I'm towing a 5k boat in the mountains. It's amazing how similar the two loads pull. Maybe its a testament to the CTD, but I'm really not sure I could tell the difference between hauling the two trailers over the same route.

I will say that I wished I'd had a gear between 3rd and OD. I'd have been plenty happy to roll along at 55-60, but 60 is 1500 RPM, which means I'm doing 80 at 2000 in OD. So I ran at 63 to get the RPMs up a bit. I will almost certainly get shorter tires next time 'round.

 

Also which no one has mentioned is that the XZT box and most of the other power adders out there will mess with the overhead computer and show much different mileage than you are actually getting. It is fooling the computer therefore the computer will not see correct information to know what is going on. Plug in the by pass and you should really see the difference. Also I personally believe that the overhead computers are not all that accurtate anyways even under ideal conditions. Most are 1 -3 mpg off from the git-go. I have only heard of a few that feel that it is very accurate. It is better as an indicator rather than a hard and true item to me.

 

Just got done hauling my 7500 lbs anchor travel trailer. Hand calculated filling to the brim got 13.2 mpg. Sounds bad but ,thats hauling up 6-8% grades at 60 - 75 mph.in the westcoast BC mountains. Smarty set on level 3 default options. Really happy with the numbers = happy camper!

 

My old 07 5.9 got 10 mpg hauling my 26' enclosed trailer loaded and 11 mpg hauling it empty. That was driving it at 65-70 mph. Any faster than that and mileage drops quick. If you want to feel better about your truck then I'll let you know that my new 6.7 gets 8-9 towing the trailer around empty (Around town).
Please let me know if you come up my way because if you drive that fast pulling a loaded trailer I want to make sure I stay off the hwy!!!!

 

Like someone else said, you should be happy you are getting 8-12 at 75-90mph. I towed 12k across country and got 14.8 MPG at 60 the whole way. Keep it under 2k RPM and you will see an improvment.