There are several liquids that we find incredibly useful on board. Let me highlight our 3 favourites at the moment:
T-9 is a fantastic treatment for metal that is (or is considering) rusting/corroding. It has saved us on so many occasions… and it keeps on working.
McLube is an amazing lubricant that is head and shoulders above WD40. It manages to lubricate without attracting dirt… and the lubrication seems to last for a very long time. For instance… If we treat our mainsail track with McL every couple months… the mainsail can drop to the boom in one shot (as long as the halyard flows freely).
One Drop is our latest passion. We are just now finding out how useful this can be. In fact I am sitting on a chair that USED to squeak constantly. Not any more.