Q: How much drag do these actually save?

The drag reduction is minimal, and we will say that plainly. These are not going to transform your range. What they do is demonstrate the level of detail we chase, energizing airflow around the mirror to trim turbulence where the factory shape gives some up. Buy them for the full carbon look first, and treat the small aero refinement as a bonus rather than the headline. If you want measurable numbers, that comes from the Model Y Performance Full Aero Kit.