I used to have a porsche 912E. It had great heating and defroster but the heating pipes rusted out. I was at college and did not have the money to fix the defroster. The only thing I had was a little cold air from the blower in the car which this car was a 1976 so it was hardly anything. How I remedied this was use Rain X Anti Fog. By george it worked great and it never foged up. So I did use it as a daily driver. If you get a JPS instead it has a defroster on it. So with the defrster and the anti fog you would not have a problem. Tha was my exerience. I presently live in Honolulu and am moving back to the East cost PA to be exact. When I get my speedster I will use it as daily transportation. So you can be asured that I will be using the anti fog. It works great as long as you dont smoke in the car. I would always leave the bottle in the car and if I needed it used a little more.