if you have a black car with no tint, the fishbowl effect will destroy you in the summer. and as far as what tint, the guy that does my tint does the police officers' cars and PO officers' cars in utah, and what they all get is 5% back and back windows, %20 front (which is illegal, but not bad). if you want so you cant see in, %5 all around on a hatchback, %20 all around on a coupe, %5 all around and %50/%35 windshield if you want it so theres no chance of seeing in (very illegal, cops get upset when they cant see in through the sides, but then cant see in through the windshield either) though usually only state troopers care about tint, locals dont have tint measurers.