[Denis]

Eastwood's "Under Gone" remover and cleaner is the best thing I've found, short of using a torch. It looks and works like an oven cleaner spray, but isn't as noxious. Hopefully, you have a way of flipping your car up so you don't have to crawl underneath to scrape the crap off. If not, spread a big tarp or plastic sheet under the car because softened undercoating is impossible to remove from your floor, hair, clothes, etc.