I'm using it on my 121 (since a year ago). In my city all cars use this stuff as a antirust coat protection (we are near to sea and the humidity here are 95-100% - and rust destroy the metal on only five years if you don't take protective measures). But first you need to unrust and paint the metal. I use it on the external underbody of the car, never into the engine bay (exhaust hot make it a messy grease - and, of course, asphaltic can be flamed). The smell goes away on few days. I don't know if it is good as a internal seal on the habitacule (i use a sheet of something like kapok glued on the firewall as sound deadener) .

Joaquin
Rojo 121 Amazon
Lima-Peru