Want to find the ultimate underbody corrosion protection,
Thats what the fella that sold me mi land rover said.a mix of doosul and old injun oil
The only problem with that is that it will wash off fairly easily, plus it's very messy....but it will do a good job if regularly re-applied. I'd advise against OLD engine oil though as it has all sorts of nasty things in it and you don't really want to be spreading that round your local roads.
i know of a few old farts that use doosul and injun oil and it dunt make a mess if left to dry..ish before driving it. and they only apllied it once with a few touch ups if needed.