[ptr]

Hello,
I have a Suzuki Swift with a 0.32 drag coeficient and i want to do some aero mods. I've lowered it by about 1inch. But from what i've read here the major problem is the back of the car. The problem is that all of the rear spoilers mounted at the edge of the roof are pointed upwords, so will increase drag. But there is a genuine spoiler mounted at the middle of the back, is it helping or is just for look?
I live in Romania, Europe, and here the fuel is pretty expensive.... around 1.1$ per litre.