Same here, 29' TT, Not going as far but here are my TripComputer and Hand calculated numbers:
Total Miles:217.2
Gallons:18.513
MPG:11.73
CPG:2.249
CPF:41.63
CPM:0.191
tc:mpg:11.6
tc:time:6:43:00


This was basically an up-hill trip from Russellville Arkansas to Eureka Springs Arkansas. Filled up before I left Russellville and filled up again right before leaving Eureka to return home. ALL 2-lane hiway and hills. I don't know the weight on my TT. This was my first "pleasure" trip with the trailer and I was quite happy with how everything worked out. I have towed the trailer other times but it's always been tow and park for several months, then move again. This was my first weekend trip.
It always amazes me how my trip computer and hand calculated mileage is always so close. I thought the trip computers were notoriously wrong.
-Tim

 

Last weekend I pulled a 2-place ATV trailer up North and back. 513.4 miles round trip. Nearly 3 1/3 mpg difference!
Trip Computer/Overhead Display showed 19.00 mpg.
Calculator showed 15.679 mpg.

 

That sounds about right.

 

Looks like the difference is due to the sig imbodie all stock and Jaxom has a smarty.
You lie to the computer it lies back.
As far as the mileage budget for 10 be glad at 12 extra spending money over 14

 

My truck rolling 35's and 3.73 gears pulling a pretty tall 31' that comes in over 10K.

I get 7.2-10. But I roll in the left lane and keep the speeds about 5-10 over posted on avg. The 7.2 is on a 250-300 mile trip with strong headwinds at 5-10 over posted interstate speeds. I'd say avg 75mph at least.

I really need 4.10 gears so I can tow at the proper rpms/speed.


I'd like to see what it would do pulling at 65mph but I've got a lead foot.

 

I thought that might be the problem except that the tire size Smarty recognizes is the stock size. Also the speedometer and odometer are accurate per a GPS as well.

I don't view the Smarty Jr. as lying to the computer so much as changing the programming parameters. Allowing more fuel is not lying. Changing the timing is not lying.

 

I recently got 13.5 towing 16K total weight on the flatlands of Ill then dropped to 9.30 in SD w/a strong 50-60 headwind
stock 98 in my sig

 

I have similar problems as you with the 3.73's and 35's and lead foot. Mine has been getting between 8.6-10.5.

 

When you do your hand calculations make sure you compare your odometer with actual miles driven. It is amazing how much change takes place just from tire wear. I like to check the mile post against the odometer and like to go a good 100 miles or so, nothing much else to to anyhow. BTW yes I'm an engineer and am always playing with numbers....so what .

 

25 ft. trailer not 35 ft. Now I have upgraded to a 11,5k fifth. So now I am wondering if it will be around 12 0r 13 @ 65mph. I dont have an airdam for the roof of my truck.

 

I could not tell what you are driving, but 10-12, depending on head winds, is about avereage. Dropping to 60-55 may give you 1-2 more mpg. Unless you have to haul butt, try going a bit slower, will save you some fuel. Air your tires up max, too!
Have a safe trip!
Where are you going?

 

Oh, its the 91.5 home-made flatbed. I go back and forth to fl, like to know what I might get. The drivetrain and engine are cherry, and I added a 53 gallon fuel cell behind the cab. It's extermely ugly, but effective. I ran up to pittsburg nh last weekend from mass, and got 16, but I think I did some math wrong or maybe the fuel calc wrong. Its mostly uphill all the way.

 

The time I got in the low 7's was pulling a big travel trailer out of the group following another 5.9 cummins, 6.4 Powerstroke and LMM duramax with them pulling about 7-8K each. We were in a hurry. At some points we were doing 95 for good distances.


Up I45 and east over to jacksonville. Lots of hills if you've ever been.




Cummins did really well. I had an 07 4.8L 1500 Chevy with a 2500lb trailer and 1000 in the bed who was following me... He kept calling me telling me he was gonna burn up his transmission . My transmission never got hot but I watched the gauge. We lost a few in our group pulling similar trailers that the chevy was pulling!




With the 35's it's a pain in the hills shifting it in and out of over drive. I got use to hitting the Haul/OD button twice and giving it sec to think then mashing the throttle only to shift it back into OD a few second later. That's the only time the tranny heated up over 190.


Oh and my bed was full of firewood as well