Undercoating was a scam at car dealers for decades... until people caught on, It has disappeared for a while, so I will not be too surprised to see some version of it coming back... someone is going to figure out how to make it sound like a positive thing again...
Do as common sense would indicate. Wash the underside of your car, as often and as thorough as possible. ... Allow it to dry and don't apply anything that can trap moisture along with road grime... :smile:KennyV