Makes sense to me. I drive old cars and keep them going for decades, it's what I've always done. Passenger vehicles don't last very long anymore. EU cars get too expensive to maintain after 300k km, and US cars were never much good after 100k mi. The Germans invented the unibody car, and also decided salt is more important for critical safety on the autobahn than the rust or environmental costs, so the cavity spray treatment was standard practice for preventive maintenance. It was a winterization preparation, just like winter tires, that people did every year or two. Now, cavity spray is mostly used by hobbyists and collectors keeping old vehicles going.
I bought a few cans of cavity spray this winter. I had to order it and pay more than I wanted to. In DE, I could go to any local hardware store and buy it off the shelf. I spent most of my life living in dry parts of the US where rust doesn't happen, but a couple of years here (2m rain/year) and I'm pulling out the big guns.
