Why not just put a windmill on the car and reduce CO2 by increasing efficiency? Well, this doesn't actually work because the drag of the windmill, even if you

Why not just put a windmill on the car and reduce CO2 by increasing efficiency? Well, this doesn't actually work because the drag of the windmill, even if you do something clever like put it in a tunnel, costs more than the energy recovered. Even an EV is still running mostly fossil based energy on average. Drag is the big energy cost on a vehicle. Anything you mount on the vehicle to purposefully catch air is going to be a net negative.