My Bro-in-Law is a retired USAF Jet mechanic and jet shop boss. He always said that jet fuel is ideal for rust situations like this. It is a thin cheap oil. It is a lot less expensive than most of the p-oils mentioned in this post. The only downside is that you will have to drive to a local airport that sells jet fuel, and ask the nice man to sell you 5 gallons, instead of 500 gallons.
