Up in Canada I've heard they spray their undercarriages with some kind of
rust preventative oil. What sort of oil is it? Does it actually work? Is it
sold in the US? Is it harmful to the vehicle in any way? I've heard it is
not legal to apply oil treatments in the US - is that true? If so, is it for
environmental, safety, or other considerations?

Having swept up about 2 lbs. worth of crumbly bits of rust during the
process of removing my engine, transmission and gas tank, I'm a bit curious
about this process.

Thanks,
Doug Fitz-Randolph
Freeport, ME