MF about preventing rust if you go ahead: i agree with wce- in my experience, Lanotec does inhibit the spread of existing rust on mild steel panels, as well as prevent its appearance in the first place. I've used their General Purpose lanolin product. (Old bikes and cars)
Good stuff,cheapish, and aussie made and owned
WD40 is mainly kero and oil (I think). Anyway, in my experience it's not very effective protection against condensation. Your Gear oil would be way more viscous so provided your engine not stored under the house in snow country (like mine), I'd guess it should work ok for at least a couple of years.
ACF 50 is a superior, aviation industry use inhibitor. Lot of bikers use it (eg for riding in UK winters- rain, snow, mud & salty roads). Has really good tenacity in adverse conditions, and is durable. You could use this stuff on your engine even if you want to use your PT for work- won't bake on/burn off your cast iron casings and barrel fins, or alloy head like gear oil. Dunno about the exhaust though. Not cheap, but brush-on and I've found a little goes a LONG way.
