Rustproofing is it worth it ?

I use Krown. It is messy but it works. My 91 Volvo is rust free and I live in the salt belt. Long time ago my father bought a new Honda Accord that he had dealer rust proffed. The crud the they used at the time dried out and developed cracks everywhere. This acted as a capillary trap for salty water. The car fell apart from inside.

I'd say stay away from it. Regular trips to the car wash place (especially in wintertime) will do much more good. Make sure to spray the steel under the car too.

I have heard that it is NOT worth rustproofing a vehicle unless it is done when new. After a year, dirt and probably some rust have formed in little crevices and the rustproofing can't get on the metal to protect it in those spots. Also, some rustproofing methods and applicators are NOT worth the money. Should you decide to go ahead with the rustproofing anyways, I would get the vehicle up on a hoist and pressure wash or steam clean the complete undercarriage before applying any rustproofing. I would do this myself if possible to be sure of getting a thorough job. Many places will take your money and give the vehicle a quick once over with the washer missing many corners, etc..