Well I think like most members on here that whatever car you own, you like to keep the bodywork in as good shape as is possible especially when you see some rust buckets on ebay. Small stone chips arise and you apply krust from hamerite as I've done recently then a top coat of paint then a lacquer or in my case a pearl topcoat. But every now and again I do wonder about the underneath. I bend right down when i do clean the car (not some kind of praying ritual) as to get to the sills
and right up to the metal strips that have the jacking points in them. But beyond there that is where I can't get to and the undersides of most cars are factory treated against rot/rust. But for how long does it last. That's where I was thinking about wax oiling the underside. I would not undertake wax oiling myself but I did some searching on the matter and found a company that does treat the underside of cars both new and old. They use a type of wax oil that doesn't stay greasy. The non greasy type is better they say as dust and grime doesn't stick to the underneath. But has someone here done a similar procedure. It seems worth it to protect the car especially as it's an out of sight area and therefore kinda gets forgotten about until you or a mechanic put a foot through a rotten rust hole in the cars floor thus your newest mod will be a Flintstones car. I also read that imported cars from Japan have none or only have a thinner coat of protectant as they don't use salt on their roads so there is not so much a need for it. I'm unsure of if this claims to be true or false. Ill post the links of this place and the statement of little or no underseal on some cars. It about the third reply paragraph down. See what you think.
Wax Oil Service http://www.westsussexrestorations.co.uk/cavity-wax-oiling
About Importing A Car And Rust Issueshttp://www.honestjohn.co.uk/forum/post/index.htm?t=90948#m1013378