How much less drag when mirrors are folded?

[SOULPEDL]

Elon on this Wed interview mentioned how having side mirrors can cause a 5% drag at highway speeds. So I tried folding them in at speed, but they don't stay there. It may only contribute to 1-2% because they are still present, but I wonder if they've measured it? I bet it would make a difference on those endurance runs through.

 

[Derek Kessler]

The mirrors are designed to be as aerodynamic as possible given that they have to be there. They're certainly not designed to be more aerodynamic when folded — certainly they're sticking less when closed, but the inside face that's now the forward face is designed to be a surface that air slips past without making too much noise and not one that cuts through the air at 60+ mph. I'll bet efficiency is worse with the mirrors folded.

 

[Shock-On-T]

Very difficult to measure outside a wind tunnel. My guess would be more efficient folded, because the primary variable is cross
area.