I, for one, have always thought that the undercoating that some dealers try to sell you on a new car was useless BS. Several threads here lately have mentioned having your vehicle undercoated on a regular basis. (GML, I'm looking at you)
What are the opinions of this forum (including brand names) of undercoating methods that are most likely to help ensure a long-lasting vehicle?
The value of undercoating is dependant on several factors. One is where you live; getting undercoating is a waste if you live in SoCal for instance. In the northeast where we dump more salt on our roads than some countries consume in a year every winter it's value is obviously higher. Most likely your van will go 7-10 years without any rust if you don't undercoat it. If you don't plan on keeping it that long, that also influences the value equation. Rusting after you sell the thing is someone else's problem.
I believe in barrier protection. The gooey cosmoline (sp?) on our VW Eurovan has kept the underlying metal in good shape over the past 14 years of continuous service here in Wisconsin (majority of driving is in winter with 3 boys in travel ice hockey)
I can definitely tell where the road spray etches the Cosmoline off and I replace it with generic "spray rubberized coating". I will spot treat these as metal is exposed. When temperature permits, I have an undercarriage wash monthly through the winter. The pictured body pan areas you have shown above really don't get rusted. The exhaust does, and overspray rubberized coating stinks when it burns off. My Eurovan floor pan at that area looks like galvanized metal but without any rust. Areas that are least protected are at the lower, outer corners where floor pan meets the painted side wall or sliding door. I struggled with those and unfortunately, rust has made an appearance into its 13th year. Good mud flaps make a big difference, so I have them on our Metris, and just the fronts.
Bottom line for me:
-spot treat vulnerable areas with a sacrificial layer of rubberized paint,
-clean salt off routinely in winter,
-mudflaps are your friends.
I bought cheap chinese ebray set of 4 mudflaps specific for Metris for $39.00 and installed the fronts in 10 minutes total.
I have to say modern paints and coatings have come along, underbody rust is almost a thing of the past.
But, Max Asst, gives good advice.
So, does Confucius-'An ounce of prevention is worth a pound of cure'. Though how he got Western measurements is beyond me.
Modern paint is awful, honestly. My W124 had much better paintwork than the Metris.
That being said- washing your car in the winter is a generally bad idea. Undercoat it before the winter, and give it a good hand wax job, and don't touch it until the snow stops flying. The chemicals auto wash shops use will at best do nothing, and at worst wash off some of the wax and undercoating.
When I was in the service all we use to here was Two words from the mechanics and Sargent's was "PREVENTIVE MAINTENANCE" and that was for all equipment and vehicles... This was in the 80's and our trucks were about 30-40 years old then with no Rust!!
I wax before and after winter and will wash on any nice day jan. or feb. to get the salt off..