I have a 90 SS truck I did a complete on a couple of years ago. I used spi black base and universal clear. I saw the truck last yr. and it looked good as the day it left. It is rarely driven or even taken outside. 2 mo. ago he decided to sell it and took it out of his shop to take pictures. It has set under the trees all that time. There was never any wax put on it with the exception of maybe some show car #7 glaze. he drove it by the shop one day and I told him to leave for me to clean up. It had tree sap?? from pecan trees really bad on the hood and top. It looked more like mildew to me. I just don't know. I washed it with HOT water and dawn 3 times. That didn't help much. I used a clay magic bar. Didn't work. Alcohol no good, urethane reducer helped tiny bit. I went over the hood with some with Chemical Guy's v32 and # 7 glaze. It looked 90% better. After a day out side then back in the shop for a week I washed it again and it looks almost as bad as it did when I started. I think I will have to repaint and wounder how far down do I need to go. Sorry this is so long. Help.