I had 20% on my jet black E92 328 with black leather, it looked great. The only downside was the highway patrol in CA are super picky with tint on the front windows that dark and issued me numerous fix it tickets. If your state allows such a dark tint on the front windows I'd go for 20%. I have 30% all around on another car, and I feel that it is too light.
Thanks for sharing this useful information
