Yeah i get your mpg with a thule rack with fairing, but my speeds are higher...When I mentioned that the roof rack takes off 5mpg all the time, I should have mentioned that I have the VW-brand roof rack. It seems to sit pretty high over the car and makes a lot of noise.. throttle position is noticeably deeper at cruising speeds. I think it is less aerodynamic than most other racks I've seen. As far as documented losses go I can only use my memory... but the several tanks I filled with my rack left would have averaged to about 41-43mpg. I remember that most of these miles with the rack installed were at only 55-60mph! Without it I would have been at 45-49mpg.
What kind of rack do you have? I borrow a Yakima rack for kayaks sometimes, and I NEVER drive around with it on without the boats, because it costs me 3+ mpg (even driving slower).
Plus it takes less than 10 minutes to put on and less than one to remove! So easy. I am always surprised how people leave their racks on 24/7 - unless its intentional for style. Lots of that on vortex.
Don't even get me started on douchers with SUV's that are afraid to pop those little half-curbs...It's a big West Coast thing too. People like others to think they are really 'outdoorsy'. Hence lots of 4X4's and jacked up 'off-road' vehicles that never see a single speck of mud in their lives, too.