Particularly the windshield. I've tried many different kinds of glass cleaners including the highly reccomended INVISIBLE GLASS. I think I have it clean and the next time the sun hits it, it's just a smeared as ever. I don't want to kinow if it comes from the dash material, the AC, my breath, etc., I just want to know how to clean it!! Someone reading this post knows the secret. I hope he/she will sharte it with the group.