I've been a TC guy(still have) and I just bought a 19'Toyhauler. The reason was the tank capacity as I boon dock all the time and usually at least a week or two. Showers will be nice after riding off road. My question is it has 100 gal. fresh tank and that's appx. 1200lbs. I drive a Duramax, How much do you think the difference in milage is with full water as apposed running empty? I ask cause a lot of times I can see finding a place to get water could be a real PIA. Also I'll have a empty truck to use.

Unless you are going up and down a LOT of hills or mountains, or doing a ton of starts and stops, then the weight of the water will not make any difference in your fuel mileage. It is the frontal area of the rig that makes the difference and the speed at which you tow it - not the weight. Once that weight gets rolling it takes very little HP to keep it going.Barney

BarneyS wrote:Unless you are going up and down a LOT of hills or mountains, or doing a ton of starts and stops, then the weight of the water will not make any difference in your fuel mileage. It is the frontal area of the rig that makes the difference and the speed at which you tow it - not the weight. Once that weight gets rolling it takes very little HP to keep it going.Barney I tow it about 60-65 when possible. I know what your saying so what would you estimate the difference if driving mountains? I live in the desert but I go to the mountains, everything is up from here...

You wont be able to figure a difference with 1200# added weight.

No noticeable difference. Wind resistance is by far the most significant factor in gas mileage for speeds over 30 mph.

I have 10 years of data when towing my old trailer with my 06 DuraMax. 12 MPG over the years average. Bought a new trailer that is taller and 4K heaver. In a 1,100 mile trip with quite a few mountains I got 1.3 MPG less. 10.7 MPG. Speed was around 65 or so.Barney and the rest are telling you the truth.

MPG difference? | Good Sam Community

20 Replies

drsteve
Explorer
Oct 21, 2017
Wind conditions on a given day will make more of a difference than a full water tank.
atwowheelguy
Explorer
Oct 21, 2017
100 gallons of water weighs 834 lbs.
Grit_dog
Navigator III
Oct 11, 2017
wing_zealot wrote:
I would be more worried about how securely that tank is supported. 1200 lbs bouncing down the road at 65 mph may leave that tank laying on the ground behind you.

Sort of defeats the purpose of having a tank if you have to fill up after you're there....
blt2ski
Moderator
Oct 11, 2017
You will need about an additional 3 HP to move 1000 lbs at 60 mph. Not a lot of fuel. An additional 3 swag ft if frontal area, also takes about 3HP to over come additional with d resistance....
Marty
N-Trouble
Explorer
Oct 10, 2017
Where did you find a 19ft hauler that has 150gal water capacity? Wouldnt think its possible.
Sandia_Man
Explorer II
Oct 07, 2017
We have a 3/4 ton Chevy gasser to haul our 32' TT TH around the four corner states and mountain west region of the country where we live and RV most often, there is a difference in mpg when our 2 freshwater tanks and both fuel tanks for generator and fuel station are full, we don't always bring toys along.

I would think the difference would be even smaller for a diesel tow vehicle, depending on what type of RVing we plan to do our rig can vary in weight by over 2K#. We always carry at least one tank full of fresh water even when going where water is available, our TT TH is 7.5K# dry, 10K# wet with toys in rear.
ktmrfs
Explorer III
Oct 07, 2017
about as much difference in mpg as the mileage difference with a passenger or not when driving empty.

I have a 7x14 ft cargo trailer, 5,000lbs and a 34ft TT almost 10K lbs with a much larger frontal area than the cargo trailer.

I get 10-12 mpg pulling the TT, and 11-14 pulling the cargo trailer.

that's with a 5,000lb difference and maybe 50 percent difference in frontal area.

from physics, at a constant speed on level ground weight difference is almost a non issue, you aren't doing any work moving the mass at a constant speed on level ground. it's the wind resistance that dominates, it's a square law function, next is tire contact friction which is a linear function.

weight will have an effect when starting and stopping, changing speed, going up a hill, then you are doing work.
wing_zealot
Explorer
Oct 07, 2017
I would be more worried about how securely that tank is supported. 1200 lbs bouncing down the road at 65 mph may leave that tank laying on the ground behind you.
prichardson
Explorer
Oct 07, 2017
As others have stated it is the lack of aerodynamic shape not the weight that is the big factor. Case in point. I have both a 5500# TT and a 7000# boat on a trailer. Using the same roads and tow vehicle I get 1 to 2 MPG better when towing the boat.
tuna_fisher
Explorer
Oct 07, 2017
Thanks all, my 1st trip will be headed to Quartzite for a few weeks to visit snowbird friends. It's only a couple of hundred miles and pretty flat, be interesting to see the difference. I know the resistance will be the bigger factor. Sure was surprised how much stuff came out of the TC when moving it to the TH.