I suspect the old guy was talking of driving on dirt/gravel roads. I found this in a site on the subject. Came from "Tom's Corner." I guess it answers my question.
If you intend to keep the car for a significant length of time (four years or more) have rust protection applied by a rust protection specialist. And I don't mean just undercoating or oil spraying. Let's take a closer look at these two methods. Undercoating seals up whatever rust has started and creates a waterproof underbelly where water and rust get trapped and continue to eat away at your car. Oil spraying creates a potential fire hazard if the oil was to be ignited by hot exhaust. Also, with the first good blast of winter weather most of it gets washed off along with any rust protection the oil might have offered. It's quite ineffective, to say the least. And you can forget about the magic electrical boxes that supposedly set up an electrical field to prevent rust. These systems have been found to be fraudulent by the US Government. Giant electrical systems set up to protect bridges powered by high energy generators might offer rust protection for bridges, but a little box powered by a 12 volt electrical system exposed to the weather is little more than a waste of your money.....
http://www.americascarshow.com/tc/?a...Ol__Man_Winter