Miller,
In response to your question on why I said non-detergent. Its just what I grew up using in small engines, compressors and pumps and for keeping tools [hand & yard] lubricated & rust free and the seals alive in an ancient Benjamin pellet rifle/slug gun & bicycle pumps too. 30wt. non-detergent is fairly thick & does not run, leaving a good protective oil film on surfaces wiped down w/it. Not permanent by any means, but its good for a while.
There is nothing advantageous in using a multi-viscosity or detergent mineral oil. I've heard it said that one of the additives is sometimes calcium in those oils and if so, that is hydroscopic so it might aggravate/encourage rust rather than preventing it, if left over some extended period of time. I dunno, just saying.
Guns & engines are both internal combustion devises, but their lubrication needs are quite dif. and here we are only discussing motor oil as a rust preventive.
And in that sense, oil from an engine's dip stick regardless of type would serve as well for a short term preventive if nothing else were available at the time. I've done that, on more than one occasion.
Eezox, that I first learned about from Researcher and that Stan speaks of is a synthetic rust preventive that meets some rigorous mil. spec's and is said to build up a more effective to near impervious coating w/each use. I dunno; it was about a hundred dollars for a gallon when I bought it, but that's been a long while back. I was going to share some of it w/Cowboy, but he sadly left the range while it was on its way down to me. It is a very good product. Now I hope to live long enough to use it all. ;-)
Ain't got there yet.
