Living in western NY I know that winters are horrible. I've used this stuff called Fluid Film. The stuff is simply amazing, it protects against rust and can even remove scaley rust from brake lines and other metals. My Dad sprayed the underside of his Suburban he got in NC. Three NY wintrers later it still looks like it did when he bought it in NC. Supposedly it was used exclusively in the Army, but recently became available to the public. That's why you don't see rusted Army vehicles.
2014 Base GT, M6, Brembo Brake Package, Solo Performance Mufflers, resonator delete, JLT Catch Can, Steeda Sport Springs, TrackKey