If you have yellow headlights, it does not matter how bad. Follow the instructions, don't get it on paint and don't let it dry before you wipe it off. The moment you make that first wipe you will be amazed. I was amazed. My headlight looked brand new! It doesn't take 10 minutes to do both headlights. I am going to use it again because it seems I missed a couple spots. This time I will shield the car around the headlight. No longer a 10 minute job, but they are absolutely correct; you do not want to get it on paint.