I did on my S4 and prior car, 1989 Porsche 928 S4.
Here in Dallas it appreciably reduced interior temps in summer. Barely visible unless you really look for it. I never had anyone notice it unless I specifically pointed it out, damned near 100% optically clear.
Dont remember specifics but it blocked something like 70% of UV and IR
What I had done is NOT tinted whatsoever. It is optically clear and serves as a block for IR and UV rays (around 68% if memory serves).Some States are very touchy about which windows and how much tinting. In New Jersey you CANNOT tint the windscreen or the driver's window. They also regulate how much tinting and sometimes they actually measure it. Other States are more lenient, especially as you head south and west. Before spending the money you should check the rules in your State.
True BUT I can say that when I had done on my car and prior (1989 928 S4) unless I told someone it was on there and then they looked really hard nobody could tell it was there. 100% clear? No but damned close.The 3M product appears clear, but it is not.
The lower tint seems acceptable to me though.