My Suzuki Swift is quite highly specced so it has a small roof spoiler at the back. What I don't know is whether it has a negative, a positive or a neutral effect on my fuel efficiency so to the more experienced members; which do you reckon it is? Would there be any benefit or losses if I sealed the gap between the top of the tailgate and the top of the spoiler? I don't really want to remove it as it would leave holes in the tailgate where it is bolted in place.
