I use the Yakima "load warrior" with fairing. Loaded I get about the same mileage at 65mph vs. 75mph unloaded. I seem to average low 20's no matter what I do. I plan on a 275 mile pit stop which works out well traveling with our Golden Retriever. The Tribeca range has been disappointing but I love the car and plan to keep her quite a while! BTW, this is my 3rd subie.
Thanks for the info. I manage about 22mpg @ 75 mph, any slower than that on 95 South you are taking your life in your hands. The trucks will run you right off the road. So if the mileage dips below 20 I may as well buy a bigger SUV. I do love the vehicle but the range is dissappointing.
I had a Yakima roof rack that I used with our Forester. It was the longest one they made, but was only 1/2 wide. Worked perfectly on the Forester, but was too long for the Tribeca (the back door wouldn't open up-the spoiler would rub). So, I picked up this carrier. It was sold by Subaru for the Forester. Original price was $280 or so, I found it on Craigslist locally for $80. I had to drill new holes into it to get it to fit the fixed Tribeca cross-bars, but it worked perfectly on our recent trip from NY to SC.
We made the trip this year and had the carrier on top, and a 6-speed transmission package in the back (400lbs) plus our luggage. New oil change and new Perrin air filter. We averaged 20.4 MPG over the 1850 mile trip. That includes a week of travel in Myrtle Beach and at least 3 hours of stop and go traffic on 95.
We made the same trip last year without the carrier, and without the transmission (-400lbs) and averaged 23.1 mpg. SO, there is a difference, but not that big of a difference.