I tested your theory on rental cars and always being able to tell the smokers cars. I rent cars regularly for business. Always through the same company. They tried to charge me once for smoking in the car. I hadn't. They said that they saw me smoking but not in the car and that they assumed I had smoked in it. I hadn't. Next time through the same office I purposely didn't smoke in it, sprayed some junk air freshener in it, turned it in. They tried to charge me for smoking in the car. Their reasoning was I had sprayed air freshener to hide smoking in the car and they smelled the air freshener. I hadn't smoked in the car. The next time I turned in a car at that office I purposely got out of the car, lit up a cigarette and blew all my smoke towards the open window. As the manager came up to check it in I told him to go ahead and try charging me for smoking in the car again. He didn't. I now get a deeper discount out of that office and I smoke in every damn car I rent from there. If you think you can prove that I smoke in any rental car I drive your welcome to try but it is a bet I'll take.
Oh and they switched me to trucks or jeeps, had a 2012 Ram last time. Brought one of their cars back, it only had 56 miles total on it, covered in mud.