How much does a roof rack decrease gas mileage?

Question

I have a 2004 Honda Pilot with a factory roof rack. I purchased a Yakima roof rack system (lowrider mounts, crossbars, bike and ski racks, and a wind fairing). I'm really happy with the rack; it's durable and easy to adjust, but a pain to take off and put back on. I'm considering just leaving it on all the time, but I'm wondering how much of a fuel economy hit I take with the rack installed. I've calculated my gas mileage, but I am getting crazy results--rack on gets better mileage. I think it's probably because I drive the car less with the rack off. I usually take public transit when I commute to work, so I don't drive the Pilot that much during the week.

I know that there has to be some fuel economy hit, because the car is less aerodynamic with the rack. I just don't know how much, and I don't have the time or wherewithal to actually try to precisely measure it. If I keep the rack system installed, is there a configuration that minimizes drag? Any advice would be appreciated.

Answer 1

Consumer Reports says it's 2-3 mpg at highway speeds.  More than the AC.    I wonder if they mean with the luggage attached.

Answer 2

Anything between 2%  and 5%. A lot also depends whether you are driving into or against the wind. I had some on driving into the wind they made so much noise I thought the wheel bearings had gone!

Answer 3

dont sweat the small stuff you can get better mpg perhaps 100mpg or better roof rack and all. interested?