i have a 1999 lumina in mint no rust any ware. i was going to undercoat the car but i was told Do not undercoat the bottom at all. The new cars have zinc coated metal and undercoating traps water between the surface. The manufacturer has done what is best for it already. Your just wasting material. if this is true then why do i see so many 90-01 lumina's with rotted out rockets and quarter panels ?? what can i do to keep my lumina's rockets from rusting out??