The topic of "rust" is a relative term in that if you own a rust free vehicle you want to keep it at bay, but if you have a vehicle with rust, then how much rust can be anything from rusted floors, hood, doors, rockers, to only surface rust on your frame. It all depends on where you live and how you take care of your vehicle.
The problem is that with most (all?) vehicles today they have inner and outer panels, so you can say your vehicle is rust free, but behind those fenders, etc., where you canNOT see there can be a little bit of rust, or just a wee distance behind that outer panel can also be a lot of rust.
SO I owned a Toyota FJ55 Land Cruiser that had the rust as depicted in my first sentence (everywhere). I finally sold it to a farmer who would only run it on his farm as the running gear was fine, but it had holes "everywhere".
SO I was VERY motivated to preserve my next purchase, an '86 Toyota Land Cruiser FJ60. So over several years, I bought cases of Penray Chain Lube #7006 because it sprays on as a liquid and flows nicely, but then becomes sticky. I sprayed it everywhere, removing side marker lights, headlights, rear lights, using the "straw" to spray it up into the weep holes for the rockers, doors, etc. until it leaked out onto the ground. And I did this yearly; this vehicle is now rust free in spite of driving it for years in eastern Pennsylvania winters. I also washed the underside of the vehicle in the winters, especially in the rear area fender wells, fenders and rear bumper where the tires throw up road salt.
I now use Fluid Film for the same purpose. It flows into corners and nooks and crannies. Great stuff.
Where I do have rust (on another vehicle) I de-rust, apply metal prep by POR-15, then apply POR-15 to the surface, it hardens like iron.
