Re: Underbody Coating
I investigated this as well. My understanding is that the underbody parts are coated from the factory, which is something that wasn't being done in the old days. As such, some argue that undercoatings are useless because parts are coated from the factory.
There are two basic type of undercoating.
The first is the type that creates a hard coating and forms a barrier or shell. This undercoating, when done wrong, will clog drain holes or not adhere properly, creating areas where water will sit and cause your car to actually rust faster. It's important for this type of undercoating to be applied by professionals who know exactly where your car's drain holes are (to mask them during spraying) and who apply the undercoating when the vehicle is bone dry and in a warm dry environment. It's important that there is no moisture to cause adhering problems.
The second type is oil based undercoating. Some argue that these are the way to go because they remain a liquid, repel water, and eventually wash away. That way if it gets into a drain hole it's a lot less likely to clog it. But you have to re-apply them yearly.
I didn't undercoat my last car, a 2003 Murano, and it lasted 10 years. It had a rusted sub frame piece that needed replacement and most of the original control arm bolts were frozen with rust, but the frame itself was fine. I also rarely washed it during the winter so it sat coated with salt for much of the winter.
For the Jeep, I decided that I would go with the relatively simple strategy of washing the Jeep once a week, during the winter months, using a touch-less car wash.
2014 Jeep Grand Cherokee Limited 4x4 3.6L v6 Billet Silver, Black leather interior (new)
x 2003 Nissan Murano SE AWD 3.5L v6 Sunlit Copper, Black leather interior (new)
x 1995 Ford Mustang 3.8L v6 Automatic Silver, Red cloth interior (used)
x 1986 Mercury Lynx 1.9L 4cyl Manual 3-door Hatchback white, grey cloth interior (used)