Auto Rust Protection

Rust Proofing & Undercoating?
I just bought a brand new 2012 Volkswagen GTI. My brother owns an auto shop and offered to do rust proofing and undercoating for free on my GTI as favor.
Now from what I’ve read, all VW cars come factory rustproofed. Also I’ve been told that the undercoating voids the 12 year rust warranty on the car. However, the warranty only comes in effect if the rust is bad enough to cause a hole. It doesn’t cover surface rust.
So my question is, should I take the free rust proofing and undercoat anyway for extra protection? Or is it not worth it to void that warranty. I live in upstate New York and the winters get pretty nasty here.
I live near the great lakes also. Take the rust proofing if nothing else it will act as a sound proofing and besides I think that the warranty only covers rust starting from the inside out. As for the warranty from the outside in that would be your responsibility to take care of that….you will love the car as my son has a older one but loves it…….Steve
DIY Auto repair: CounterAct