Wifes 2000 Caravan has severe rust issues (my bad). I have a 2004 Ram 1500 that's still pretty clean and I want to keep it that way. What's the best method of prevention. Is it washing once a week in the winters to remove salt? There's some guy in town that sprays oil underneath(he recommends spraying twice a year). After it's sprayed he recommends driving for a while in dusty dirt road to encrust the oil with dirt. Sounds pretty sloppy to me but lots of locals do it. Or do I just check for rust spots every summer, sand and paint over?