Trailer Height and Mileage

[Parshal]

Does anyone know how much raising or lowering a camper 1 1/2 inches would affect mileage due to wind resistance?

 

[Boldt's Wagon]

About 0. 1 mpg. If you have the Excel spreadsheet, you can download a milage calculation spreadsheet for the Cummins from:



http://www.nwbombers.com/board/ikonboard.cgi?s=3e99fca618a87e17;act=ST;f=4;t=1049

 

[Parshal]

I can't tell for sure, but just changing the height from 8. 5 to 7 I see a 1 mpg change at 70 mph and 15 mph headwind (using 3rd gear locked for comparison). I have the 5 speed so I don't know if that makes a difference. With no headwind I see pretty much no mpg loss. Looks like wind makes the difference.



I tow a lot in the wind. I'll have to look closely at this but I may be better off lowering my camper back down the 1 1/2 inches and dealing with the hitch being too low (reese weight distributing hitch).



Thanks!

 

[KKaiser]

Wow,. that's an amazingly accurate spreadsheet! last week I towed into a mean ass head wind and using the parameters of the sheet, came very close to the 8pmg that I actually got. Nice work.



Kent

 

[Okie-Go]

One more reason why I like the wing I have on the top of the truck when towing. It does make a difference. Ask an over the road trucker if he has driven one without the air dam on top. He'll tell you they do make a difference.

 

[AlFischer]

Interesting spreadsheet. But how do I save it? It requires a password.

 

[ImagesThatSing]

Originally posted by Al Fischer

Interesting spreadsheet. But how do I save it? It requires a password.

In order to save it, I just copied the contents, then pasted the contents into an open, blank Excel spreadsheet then saved it to our computer.



FWIW

 

[Parshal]

I got anywhere from 8. 5 mpg to 12. 5 mpg this weekend towing from Denver to Perdum, NE. I was a towing a 3600 lbs. travel trailer about 8. 5 feet tall. Winds were crosswind not direct headwinds either. This seems extremely bad.

 

[RustyJC]

Well, if it helps, we tow a 13,500 lb 5th wheel that's about 12'4" tall plus a front A/C unit. Towing in mixed flat/hilly towing (Houston to Fredericksburg in the Texas Hill Country), we get around 10 to 10. 5 MPG.



For comparison, our V-10 3500 got around 6. 5 MPG pulling the same 5ver over the same route.



Rusty

 

[Parshal]

Originally posted by RustyJC

Well, if it helps, we tow a 13,500 lb 5th wheel that's about 12'4" tall plus a front A/C unit. Towing in mixed flat/hilly towing (Houston to Fredericksburg in the Texas Hill Country), we get around 10 to 10. 5 MPG.



For comparison, our V-10 3500 got around 6. 5 MPG pulling the same 5ver over the same route.



Rusty

That makes it even crazier that I'm getting the same mileage with a trailer that weighs less than 1/3 of yours and is four feet shorter! What in the world is going on?!

 

[roadranger]

Originally posted by Parshal

That makes it even crazier that I'm getting the same mileage with a trailer that weighs less than 1/3 of yours and is four feet shorter! What in the world is going on?!

It's the HEIGHT of the trailer . Doesn't matter much what the length is.



Pushing something 12'6" tall down the road is going to EAT fuel!

 

[Parshal]

Originally posted by roadranger

It's the HEIGHT of the trailer . Doesn't matter much what the length is.



Pushing something 12'6" tall down the road is going to EAT fuel!

Yes, but mine is only 8' 6". It's four feet shorter in height and I get worse economy.

 

[Dieselnerd]

Interesting, my 5th wheel is similar in size to what Rusty is pulling. Average weight around 13000 pounds, length 35 feet, height around 12 feet. I average 10 mpg running 65 mph. In a strong headwind it's gone as low as 8 and with a strong tailwind it's been as high as 12 but I can usually count on 10 mpg most of the time.

 

[brobeson]

Towing and MPG

AS you know I tow RV's for a living putting on about 15-20K miles a month.



Here is what I have found.



Cab over campers get better mileage if you put that cushion between the cab top and the camper. I get about the same MPG with small or large campers.



5th wheels get better mileage than do travel trailers. We even get better MPG with a 5er than those "V" nose utility and horse trailers of similar weight.



The difference in size has to get pretty big (like a 35' 5er vs a 22' TT) before the TT will match the 5ers MPG.



MPG drops off quickly after 65 MPH.



60-65 I can get 12mpg

70-75 I get 8





And of course, the heaver that trailer the worst the MPG, but mostly only when climbing hills. On the flats I can't tell the difference. I travel I-5 in California which is flat for many hundreds of miles.



Bob

 

[Whitmore]

I know the use of a wing is the ultimate answer to wind drag but I was also wondering if those airtab deals on top and back of the cab would help any? I tow a 27 ft. 5er and it was to my surprise that a couple of 2x8's about 2 ft long blew out of the back of the truck at 65 mph and this was on a calm day



cheers, Kevin