|
Spoilers and wings are two different things.
Very generally speaking, spoilers typically decrease overall drag by redirecting airflow in such a way as to shrink the area of low pressure at the back of the car, or reduce any natural lifting tendencies.
Wings create downforce which is lift in a downwards direction and a natural byproduct of lift is drag. In the end, your friend is right, any functional wing will increase drag. It won't be particularly effective at anything other than highway speeds and above, and the rest of the time it's a big chunk of plastic sticking out into the airstream.
The OEM spoiler actually decreases drag and would consequently marginally increase mileage. But, if you're going for the Superbird look, then just pick the one you like best. It's hard to imagine any option will make more than a couple mpg difference.
|