I just installed a BMW rear view mirror. Isn't there some sort of solvent to remove the mirror mount that's glued on?

The original on the car was stuck with a patch that comes off with a razor blade. If mirror glue was used usually a razor blade started under it will lift the residue off.

Heat gun and a razor blade. Or you could just then replace the winsheild..

Thin Slim Thin Flexible Putty knife sharpened slightly then dulled slightly to thin it at the edges. slip in behind base and dig into the glue from all sides and it will comes of in minutes or less. I have done this four times now with same cheap putty knife and actuall only takes a minute or less now.. Razor blade and windex to clean off any residue

mek always works

Put the putty knife under the mount, tapped it once and the thing popped right off. Cleaned up great with a razor blade. Thanks.
Cheers, Elliot

This is unusual. Ordinarily they just fall off.