When I shift to reverse, the side mirrors angle downwards automatically. The driver's side one squeaks when it does this. Was wondering if anyone experienced this and has a tip to remove the squeak.

I recently upgraded my puddle lamps to blue LEDs to match my interior lights and took the opportunity to spray a little bit of WD40 on the mechanism. I didn't use much, since the mirrors are basically friction fit I didn't think it wise to spray all over, but that didn't seem to make any difference.

The mirror still seems to move freely enough and nothing obvious is rubbing.

 

Are you saying your mirror squeaked after using WD-40 on the mechanism? If that's so, I suggest you lube the mechanism with Tri-flo which is Teflon-based and excellent for lubricating plastic.
WD-40 is not the universal lubricant it's cracked up to be, in my opinion.

 

My mirrors squeaked when they folded, and it took the dealership about 20 minutes to lube whatever was making the noise. Hasn't come back since.

 

No, the WD-40 didn't make any difference, squeaked before and after. I'll look at your suggestion.