Factors affecting MPG

[crumvoc]

The attached link from the Goodyear Tire Company contains an interesting analysis of factors affecting mileage on over the road trucks. Overall, it appears that the height of the trailer (drag) is more of a factor than is weight. Also, the larger the gap between the TV and the trailer, the more drag/less MPG. If the TV has a wind profile similar to the trailer (similar height), the better the mileage. If the TV is lower, or like a pickup without a cap is lower behind the cab, more drag. This was pretty common sense stuff but interesting nonetheless.
http://www.goodyear.com/truck/pdf/radia ... d_S9_V.pdf

[Shadow Catcher]

I have been thinking about this. Compass Rose is both wider and taller than the Subaru and I really notice a difference towing it to Indiana bucking a stiff head wind. One thing I am going to try once I have the Ultra Gage (read out, of gas consumption etc.) is to try it with a canoe on top of the car.

[GuitarPhotog]

A canoe on top of my Subaru Forester dropped the towing mileage from 21/22 down to 15/16. Lots of added turbulence, insignificant weight addition.

One data point.

<Chas>

[Shadow Catcher]

When we traveled with the canoe it was always filled with PFD's and dry bags etc, and no appreciable change in MPG. The canoe is 18'4" though we do have three others that are shorter.
I will probably be buying some air tabs and will be talking with them as to the value of mounting them on the TV http://www.buyairtab.com

[wagondude]

On my Outback, the 16'6" Oldtown angler (about 74#) only cost me about 2MPG. But I only drive 55 MPH with or without the canoe.

Bill

[pete42]

my F150 only gets between 15 and 16 with a full cap over the bed thats where I carry my mobility scooter.
when I added my 26 foot factory built travel trailer with an 8 foot high fairly flat front my mileage dropped to 9 mpg.
if I wanted to keep up with Interstate traffic 65--70 mph it dropped even lower, travel at 55 I got the 9 mpg sometimes
in the flat state of Florida I could squeeze out 10 mpg only good thing was spending a couple of months in the trailer
was great lots of room and all the goodies.

I think it was barb who when she placed a canoe on her truck rack got better mileage

pete

[jss06]

Definatley frontal area or "Sail" area.

Towed a 6x12 Uhaul pretty much loaded to the maximum weight of around 3500 lbs with a 3500 Dodge Diesel. The trailer tucks in very nice behind the truck and I averaged about 22 MPG on the 4 hour trip. It was all highway.

Same truck, same weight (approximately 3500 lbs), pretty much the same speed, but this time it was a travel trailer. 8x8 foot frontal (sail) area. I was towing on the highway through New Mexico with a nasty head wind. On this trip, I averaged 11 MPG.

I pulled 2 jeeps on a goosneck trailer (14K lbs) and got better milage than with that travel trailer. Folding the windshield down on the Jeep was good for 1MPG increase while towing.

If the trailer tucks in nice behind the tow vehicle it will increase you milage. If there is a large area that sets out in the wind flow, you milage will suffer.

[Nobody]

Frontal area of the towed trailer definitely makes a difference in fuel efficiency but IME not as much as wind. My TD 'tucks' in the wind shadow of my TV & under normal driving conditions my mileage driving solo drops from around 20-21 to 17-19mpg when towing the TD. I have a 13' Scamp molded fiberglass camp trailer with pretty near the same frontal area as the TD, just a little more curved. It & the TD weigh near the same. I've towed it several hundred miles (vs several thousand for the TD) but up to now fuel mileage has been identical with both trailers. Have not had any severe winds towing with my current TV (2008 Toyota Tacoma V-6) but had near the same fuel efficiency with the previous TV ('95 Nissan Hardbody KingCab 4X4 P/U, 4cyl w/5sp trans). Towing across NW Kansas (pretty flat country) with the Nissan & TD in 2007, we experienced 30-45mph quartering headwind that dropped my fuel mileage to less than 13mpg & I wasn't able to maintain the speed limit (55mph) in 5th gear. Some of that was probably because of the smaller, 4cyl engine but, the wind definitely made a huge difference.

Tacoma with TD


Tacoma with Scamp


As you c an see the Nissan didn't provide quite as much 'wind shadow' for the TD