beep-beep

Hey. I usually drive around with the roof rack (Thula crossbars with three bike rails in summer, snowboard rack in the winter). And usually get around 22MPG on highway. Recently I took off the roofrack completely and got 26MPG driving in the same highway conditions. So 4MPG are attributed to the roofrack with a high degree of certainty. It all was measured on 2006 A6 3.2 Avant with stock everything and decent service history; 147000 miles.
I usually drive pretty fast on highways. If you drive slower the difference can be smaller since the air drag is a cube of velocity. or something like that.

To translate 4MPG into money. It means that if you drive 15000Mi a year and spend $1500 on fuel, you will spend $225 a year in fuel to have the roofrack all the time.

Is this reasonable? I probably will consider to cary snowboards and bikes inside when it is only one or two of us going. I also will use my bosch impact driver to get the roofrack on and off quickly so I do not have it most of the time.

A6Gary

I have the Audi crossbars and a Thule storage carrier on my 2006 A6 Avant. I only use them when we go for a long ski trip because I don't have the room for both the luggage and the ski bag with the skis/poles. When I use this equipment, I notice about 2 MPG decrease driving about 60-70 MPH. Other than that, I leave them off the car.

uberwgn

yeah, the roof racks cause significant drag even when they're empty