My uncle's Fairlane sat on gravel for 12 years and the frame still looked new, so why does everyone I know park on grass
Back in 2009 my uncle parked his '65 Fairlane on a gravel pad behind his shop in Reno and pulled it out last spring with barely any rust under it. Meanwhile a buddy of mine left a Camaro on grass for just 3 years near Spokane and the floor pans were soft as cardboard. I keep hearing people say dirt is dirt and it doesn't matter what's underneath, but water sits right on grass and goes nowhere. Anyone else seen gravel or concrete make a way bigger difference than they expected?
Water just sitting there under the grass is the whole problem, and grass keeps it damp nonstop. Saw the same thing with a truck parked on gravel for years, the underside held up way better than my cousin's car that sat on dirt and got eaten up.
Man, you already answered your own question with that Reno story, gravel lets water drain straight through instead of trapping it against the metal. If you've got to park something long term, get it off the grass and onto stone or concrete, and if all you have is dirt, toss down a few inches of crushed rock first. The ground underneath matters way more than people want to admit.