I have a half pint jar of what was probably fairly thin semi synthetic engine oil (whatever was to hand at the time) which I dip small steel engine parts in before storing them. However it runs off in a few weeks leaving only the thinnest trace on the surface which damp can then get through and let rusting start. Clearly something thicker would be better, maybe gearbox oil, but what might have some 'tackiness' in it and stick to the surfaces best without being so thick it coats them and has to be cleaned off again before use?
I did toy with the idea of mixing some castrol grease in the oil to thicken it up a bit but never got round to trying it.
-- Dave Baker