Rubberized undercoating

cosmo is the bees knees
Dont waste your time and money on anything else esp the crap that washes off easily

 

Cosmo if it's still clean and looks new with no rust, that stuff is great but if there's already rust, I've found it doesn't work the best.

If there's already rust, fluid film type products are better as they will oil the metal and prevent it from getting worse. I personally use surface shield by PB blaster.

 

At work We have a fleet of about 55 Chevy express vans that get “tar” like undercoating done. These vans get abused and never get the undercarriage rinsed. I’ve been there for 10 years, some vans are 15-20 years old. Not a single rust issue on any of these vans. I’ve never heard our mechanic/manager/president mention anything about rust issues.

I think folks that say moisture/salt or whatever else “creeps in” behind the undercoating and creates “pockets” have absolutely zero experience with rubber undercoatings and are just echoing the same BS that others are saying.

They key is, to get it done properly when the vehicle is new. I had vulcanized rubber applied on my frame and bottom of my cab, 99% of it looks like new except for some rock chips and I can guarantee you nothing is “creeping in” behind the coating haha.
It’s a rust preventative coating that will not let anything rust underneath it.

This is the pic of my vans frame, looks great if you ask me. Never rinsed the undercarriage and zero maintenance/touch ups.

I do use fluid film on my suspension, rear axle, tow hitch and spare tire area.

 

Idk, never tried cosmoline on a rusty vehicle, but have used it the last 4 years year on a rusty 55 year old mower deck. It holds up better than the fluid flim I've tried in the past. If I cut wet grass with fluid flim on the deck, the abrasion thats created will wipe most of it it right off. With cosmoline it will last almost all season where I have to hit the deck with it again for next year.