chasis saver is GOOD STUFF!
i used it on the bottom of my doors on my truck which were rusting on the insides. It would eat through rustoleum after a month even in the summer, but chasis saver has endured 1 and a half winters so far and its just now rusting through again. Salt hits that spot especially hard so im impressed.
only bad thing - $40 for a quart last time i bought it at the dupont store. i need to find a cheaper place to get it.
I dont think rust would go through por 15. I think it actually stops the oxidation completely. ( I could be wrong)
Never used Chassis Saver, but POR15 I have. I like it. Wear industrial rubber gloves and do not get it on your skin at all. The smallest dot will be there for MANY days. If you spray it wear goggles, not glasses.