what i do is i let my car smell like weed. I dont care if it does, smell does not mean search if you get pulled over, unless they have the drug sniffing dog. And even then they have to find something. What i do though to get rid of the smell after smoking in my car is that i get the incense that the local headshop sells, usually between 10-20, and keep them in the plastic bag in my car. They arent nag champa ones, they are like actual incense with the "different aromas" and after a day to two the smell starts to become really strong in my car, plus when i am finished my car continues to smell like incense, and i can burn the incense in my house to keep it fresh.