So, I posted up a thread on my 09 that got 120% rusted to complete perforation, others on here same issue. Here is the thing I need and others perhaps, advice on where to go with this

On my 09 the rockers had plastic plugs in the bottom, im guessing water collects due to the plug and caused the rust. The brand new 2015 2500 I bought, same damn thing.

IS this right, does anyone know what the hell this plug does, if we need to take it out, leave it in, etc..

I was thinking of spraying some 3M undercoat rubber spray inside the rocker and once on a lift, the underside of the truck.

 

I wouldn't spray the rubber under coat on it. it eventually drys out and cracks , thus letting water in. In my opinion oil is best. I've used it on all my vehicles for years. Thats interesting about the plugs though, i'm going to go out now and check.