To definitively say if it increases drag you would have to do a complex model on a computer or actually install them and do a test with and without them in an air chamber.

Nobody here is going to do either.
The air flow around a rotating tire may affect the equation too.
We just don't know.

I am a fanatical hypermiler without splash guards.
I am pretty sure I'm going to get them for my new car.
YMMV.

Need fewer troops to support.
Drive a hybrid.
Best tank 71.65 MPG.

Before this car I spent two years learning hypermiling on my 2004 HCH1.