The wife works at True Manufacturing where they make commercial refrigerators many of which are all stainless steel.
They are insulated using spray expansion foam, they used blasted dry ice like that to clean the stainless steel to clean off what ever foam insulation squeezes out of the gaps at seams. If you're ever in a Walmart, Dollar General or a Starbucks and you see a cooler that says "True" on the front that's what they make.

It doesn't leave any marks behind like from scraping the foam away.
There is no way to remove a scratch from the stainless steel and it leaving no marks is a big deal to them since commercial refrigerators aren't cheap so they have to be perfect.
It melts away leaving no residue and is obviously food safe.

I hadn't ever thought about it being used to clean the underside of a car, but I can't see why it would be a problem.