Anothern from California, where front tint is illegal...Any amount of tint helps to cool the interior of vehicles, as well as block UV light which can degrade upholstery, etc. On two cars, I ran 20% behind the front and 95% on the two fronts.
Remember with tinting, the percentage indicates light transmission, not light blockage. 95% is nearly clear, but it cuts glare and provides a little shade to front seat occupants. On the rear, 20% is a good tint for keeping rear seat occupants cool and comfortable and dimming the effects of highbeams in the rearview.
With 20% or limo tint (5%), expect the local police to treat you a little differently should they happen to walk up on your car, as they won't be able to see inside, especially at night.
73 280 SEL 4.5