How much do the bare bars add to your fuel costs?
Short answer is I don’t know, I put the bars on when the car was new and haven’t taken them off. They are mostly not noticeable at all. They fit very neatly between the roof rails, not on top.These ones.
I have had the same bars for 3-4 years, and, similarly, I have never taken them off; my sense at the time I put them on was that they made such a negligible difference to fuel economy it just wasn't worth the hassle. The box, on the other hand, seems to add about 1-1.2l/100km! (typical open road economy of 5.4 jumps to 6.5sh.)